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href="../19287/proteins-enzymes--1.html">Proteins & enzymes </a></li><li><a href="../19291/lipids-1.html">Lipids</a></li><li><a href="../19299/carbohydrates--1.html">Carbohydrates </a></li><li><a href="../19305/vitamins--1.html">Vitamins </a></li><li><a href="../19313/biochemistry-the-environment--1.html">Biochemistry & the environment </a></li><li><a href="../19336/proteins-enzymes-ahl--1.html">Proteins & enzymes (AHL) </a></li><li><a href="../19347/nucleic-acids--1.html">Nucleic acids </a></li><li><a href="../19361/biological-pigments--1.html">Biological pigments </a></li><li><a href="../19366/stereochemistry-in-biomolecules-1.html">Stereochemistry in biomolecules</a></li></ul></li><li><a href="../19390/option-c--1.html" class="father">Option C </a><ul class="level-2"><li><a href="../19391/energy-sources-1.html">Energy sources</a></li><li><a href="../19407/fossil-fuels-1.html">Fossil fuels</a></li><li><a href="../19411/nuclear-fusion-nuclear-fission-reactions-1.html">Nuclear fusion & nuclear fission reactions</a></li><li><a href="../19429/solar-energy-1.html">Solar energy</a></li><li><a href="../19437/environmental-impact-global-warming-1.html">Environmental impact - global warming</a></li><li><a href="../19453/electrochemistry-rechargeable-batteries-fuel-cells-1.html">Electrochemistry, rechargeable batteries & fuel cells</a></li><li><a href="../19458/nuclear-fusion-fission-hl--1.html">Nuclear fusion & fission (HL) </a></li><li><a href="../19470/photovoltaic-cells-and-dsscs-1.html">Photovoltaic cells and DSSCs</a></li></ul></li><li><a href="../19078/option-d-1.html" class="father">Option D</a><ul class="level-2"><li><a href="../19079/pharmaceutical-products-drug-action--1.html">Pharmaceutical products & drug action </a></li><li><a href="../19158/aspirin-penicillin--1.html">Aspirin & penicillin </a></li><li><a href="../19174/opiates-1.html">Opiates</a></li><li><a href="../19184/ph-regulation-of-the-stomach-1.html">pH regulation of the stomach</a></li><li><a href="../19194/antiviral-medications--1.html">Antiviral medications </a></li><li><a href="../19211/environmental-impact-of-some-medications-1.html">Environmental impact of some medications</a></li><li><a href="../19254/taxol-a-chiral-auxiliary-case-study-1.html">Taxol - a chiral auxiliary case study</a></li><li><a href="../19258/nuclear-medicine--1.html">Nuclear medicine </a></li><li><a href="../19273/drug-detection-analysis--1.html">Drug detection & analysis </a></li></ul></li></ul></li><li><a href="../16592/practical-scheme-of-work-ia--1.html">Practical scheme of work & IA </a><ul class="level-1"><li><a href="../16682/internal-assessment-1.html" class="father">Internal Assessment</a><ul class="level-2"><li><a href="../18892/scaffolding-the-investigation-1.html">'Scaffolding' the investigation</a></li><li><a href="../18896/timing-organisation--1.html">Timing & organisation </a></li><li><a href="../18905/choosing-the-research-question-1.html">Choosing the research question</a></li><li><a href="../18946/personal-engagement-1.html">Personal engagement</a></li><li><a href="../18950/exploration-1.html">Exploration</a></li><li><a href="../18957/analysis-1.html">Analysis</a></li><li><a href="../18965/evaluation-1.html">Evaluation</a></li><li><a href="../18966/communication-1.html">Communication</a></li><li><a href="../19882/internal-standardization-of-the-ia-1.html">Internal standardization of the IA</a></li><li><a href="../19901/submitting-the-samples-for-moderation-2.html">Submitting the samples for moderation</a></li><li><a href="../33754/ten-suggestions-for-ias-using-secondary-data-1.html">Ten suggestions for IAs using secondary data</a></li><li><a href="../37544/gaining-full-marks-for-a-databased-ia--1.html">Gaining full marks for a databased IA </a></li><li><a href="../19506/ia-example-marking-exercise--1.html">IA example & marking exercise </a></li><li><a href="../23929/genuine-examples-of-moderated-ia-reports-1.html">Genuine examples of moderated IA reports</a></li><li><a href="../25234/examples-of-teacher-marked-ia-reports--1.html">Examples of teacher-marked IA reports </a></li><li><a href="../37542/history-of-internal-assessment-1.html">History of Internal Assessment</a></li></ul></li><li><a href="../16598/mandatory-laboratory-components-1.html" class="father">Mandatory laboratory components</a><ul class="level-2"><li><a href="../16613/formula-of-magnesium-oxide--1.html">Formula of magnesium oxide </a></li><li><a href="../16612/determining-the-mr-of-an-unknown-gas-1.html">Determining the <i>M</i><sub>r</sub> of an unknown gas</a></li><li><a href="../16615/acid-base-titrations--1.html">Acid-base titrations </a></li><li><a href="../16616/a-green-acid-base-practical-1.html">A green acid-base practical</a></li><li><a href="../16617/analysis-of-aspirin-tablets-1.html">Analysis of aspirin tablets</a></li><li><a href="../16618/caco3-in-egg-shells-1.html">CaCO<sub>3</sub> in egg shells</a></li><li><a href="../16644/enthalpy-changes-1.html">Enthalpy changes</a></li><li><a href="../16631/reaction-rates-1.html">Reaction rates</a></li><li><a href="../16635/rate-dependent-factors-1.html">Rate-dependent factors</a></li><li><a href="../16636/determining-ea-for-a-reaction-1.html">Determining <i>E</i><sub>a</sub> for a reaction</a></li><li><a href="../16637/iodination-of-propanone-1.html">Iodination of propanone</a></li><li><a href="../18144/titrations-with-a-ph-meter-1.html">Titrations with a pH meter</a></li><li><a href="../18355/redox-titration-with-kmno4--1.html">Redox titration with KMnO<sub>4</sub> </a></li><li><a href="../16640/voltaic-cells-1.html">Voltaic cells</a></li><li><a href="../16659/3-d-molecular-modelling--1.html">3-D molecular modelling </a></li></ul></li><li><a href="../17168/other-good-practicals-1.html" class="father">Other good practicals</a><ul class="level-2"><li><a href="../17196/common-chemical-reactions-1.html">Common chemical reactions</a></li><li><a href="../227/elements-oxides-of-the-third-period--1.html">Elements & oxides of the third period </a></li><li><a href="../17239/the-halogens-1.html">The halogens</a></li><li><a href="../17162/boiling-points-of-mixtures-1.html">Boiling points of mixtures</a></li><li><a href="../17170/polarity-of-molecules-1.html">Polarity of molecules</a></li><li><a href="../18083/le-chateliers-principle--1.html">Le Chatelier's principle </a></li><li><a href="../19582/determining-kc-for-an-esterification-reaction-1.html">Determining <i>K</i><sub>c</sub> for an esterification reaction</a></li><li><a href="../18164/redox-reactions-of-vanadium--1.html">Redox reactions of vanadium </a></li><li><a href="../18351/chlorine-in-swimming-pools--1.html">Chlorine in swimming pools </a></li><li><a href="../18178/analysis-of-cuii-ions-in-solution--1.html">Analysis of Cu(II) ions in solution </a></li><li><a href="../18179/percentage-of-copper-in-brass-1.html">Percentage of copper in brass</a></li><li><a href="../18356/electrolytic-cells--1.html">Electrolytic cells </a></li><li><a href="../18598/reactions-of-organic-compounds-1.html">Reactions of organic compounds</a></li><li><a href="../18752/hydrolysis-of-halogenoalkanes-1.html">Hydrolysis of halogenoalkanes</a></li><li><a href="../18784/preparation-of-13-dinitrobenzene--1.html">Preparation of 1,3-dinitrobenzene </a></li><li><a href="../19022/determination-of-an-organic-structure-1.html">Determination of an organic structure</a></li><li><a href="../19887/preparation-of-nylon-66-1.html">Preparation of nylon 6,6</a></li><li><a href="../19343/determination-of-vitamin-c-content--1.html">Determination of vitamin C content </a></li><li><a href="../19342/hydrolysis-of-starch--1.html">Hydrolysis of starch </a></li><li><a href="../19159/preparation-purification-of-aspirin--1.html">Preparation & purification of aspirin </a></li></ul></li><li><a href="../18851/ict-in-practical-work-1.html" class="father">ICT in practical work</a><ul class="level-2"><li><a href="../18852/data-logging--1.html">Data logging </a></li><li><a href="../18853/software-for-graph-plotting--1.html">Software for graph plotting </a></li><li><a href="../18854/spreadsheets-for-data-processing--1.html">Spreadsheets for data processing </a></li><li><a href="../18855/databases-1.html">Databases</a></li><li><a href="../18856/computer-modelling-simulations--1.html">Computer modelling & simulations </a></li></ul></li><li><a href="../16594/group-4-project-1.html" class="father">Group 4 Project</a><ul class="level-2"><li><a href="../16595/practicalities-1.html">Practicalities</a></li><li><a href="../16596/reflective-statement--2.html">Reflective statement </a></li></ul></li><li><a href="../16666/a-new-laboratory-1.html">A new laboratory?</a></li></ul></li><li><a href="../16284/exams-1.html">Exams</a><ul class="level-1"><li><a href="../16286/essential-facts-1.html" class="father">Essential Facts</a><ul class="level-2"><li><a href="../16287/objectives-command-terms-1.html">Objectives & command terms</a></li><li><a href="../16288/grade-descriptors-1.html">Grade descriptors</a></li><li><a href="../16289/grade-boundaries-1.html">Grade boundaries</a></li></ul></li><li><a href="../16302/paper-1-multiple-choice-1.html" class="father">Paper 1 (Multiple Choice)</a><ul class="level-2"><li><a href="../16303/advice-to-students-paper-1-1.html">Advice to students (Paper 1)</a></li><li><a href="../31515/practice-paper-1-exams-1.html">Practice Paper 1 exams</a></li></ul></li><li><a href="../16305/paper-2-1.html" class="father">Paper 2</a><ul class="level-2"><li><a href="../16306/advice-to-students-paper-2-1.html">Advice to students (Paper 2)</a></li><li><a href="../16307/areas-of-difficulty-1.html">Areas of difficulty</a></li></ul></li><li><a href="../16313/paper-3--1.html" class="father">Paper 3 </a><ul class="level-2"><li><a href="../16314/advice-to-students-paper-3-1.html">Advice to students (Paper 3)</a></li><li><a href="../16342/data-response-questions-1.html">Data response questions</a></li><li><a href="../20054/experimental-work-questions-1.html">Experimental work questions</a></li></ul></li><li><a href="../16324/the-examination-process-1.html" class="father">The examination process</a><ul class="level-2"><li><a href="../16316/setting-the-exam-papers-1.html">Setting the exam papers</a></li><li><a href="../16317/predicted-grades-1.html">Predicted grades</a></li><li><a href="../16318/marking-the-papers-1.html">Marking the papers</a></li><li><a href="../16319/commenting-on-the-exams-1.html">Commenting on the exams</a></li><li><a href="../16320/grade-awarding-1.html">Grade Awarding</a></li><li><a href="../16321/enquiry-upon-results-1.html">Enquiry upon results</a></li><li><a href="../16322/chief-examiners-report-1.html">Chief Examiner's report</a></li><li><a href="../16323/retaking-the-exam-1.html">Retaking the exam</a></li></ul></li><li><a href="../16325/faqs-1.html">FAQs</a></li></ul></li><li><a href="../3147/ib-core-1.html">IB Core</a><ul class="level-1"><li><a href="../3149/learner-profile-1.html">Learner Profile</a></li><li><a href="../21735/extended-essays--1.html" class="father">Extended Essays </a><ul class="level-2"><li><a href="../21736/overview--1.html">Overview </a></li><li><a href="../21780/responsibilities-1.html">Responsibilities</a></li><li><a href="../21790/resources-1.html">Resources</a></li><li><a href="../21800/research-1.html">Research</a></li><li><a href="../21804/writing-the-essay-1.html">Writing the essay</a></li><li><a href="../21810/assessment-1.html">Assessment</a></li><li><a href="../22434/summary-of-advice--1.html">Summary of advice </a></li><li><a href="../25272/faqs--1.html">FAQs </a></li></ul></li><li><a href="../307/theory-of-knowledge-tok-1.html" class="father">Theory of Knowledge (TOK)</a><ul class="level-2"><li><a href="../41171/the-12-tok-concepts-1.html">The 12 TOK concepts</a></li><li><a href="../3507/why-tok-chemistry-1.html">Why TOK & Chemistry?</a></li><li><a href="../3505/a-modern-paradigm-1.html">A modern paradigm</a></li></ul></li></ul></li><li><a href="../17783/fast-track-to-tests-questions-1.html">Fast track to tests & questions</a><ul class="level-1"><li><a href="../17784/sl-multiple-choice-tests-on-individual-topics-1.html">SL Multiple choice tests on individual topics</a></li><li><a href="../24351/sl-multiple-choice-quizzes-on-sub-topics-1.html">SL Multiple choice 'quizzes' on sub-topics</a></li><li><a href="../31519/sl-practice-paper-1-exams-1.html">SL Practice Paper 1 exams</a></li><li><a href="../17786/sl-questions-on-each-sub-topic-1.html">SL Questions on each sub-topic</a></li><li><a href="../20431/sl-paper-3-section-a-questions-1.html">SL Paper 3 Section A questions</a></li><li><a href="../17792/sl-questions-on-the-options-1.html">SL Questions on the options</a></li><li><a href="../24897/sl-quizzes-on-option-sub-topics--1.html">SL Quizzes on option sub-topics </a></li><li><a href="../17785/hl-multiple-choice-tests-on-individual-topics-1.html">HL Multiple choice tests on individual topics</a></li><li><a href="../24352/hl-multiple-choice-quizzes-on-sub-topics-1.html">HL Multiple choice 'quizzes' on sub-topics</a></li><li><a href="../31520/hl-practice-paper-1-exams--1.html">HL Practice Paper 1 exams </a></li><li><a href="../17787/hl-questions-on-each-sub-topic--1.html">HL Questions on each sub-topic </a></li><li><a href="../20428/hl-paper-3-section-a-questions-1.html">HL Paper 3 Section A questions</a></li><li><a href="../17793/hl-questions-on-the-options-1.html">HL Questions on the options</a></li><li><a href="../24973/hl-quizzes-on-option-sub-topics-1.html">HL Quizzes on option sub-topics</a></li><li><a href="../41573/printable-versions-of-written-tasks--1.html">Printable versions of written tasks </a></li></ul></li><li class="selected"><a href="../41465/complete-course-for-students--2.html">Complete course for students </a><ul class="level-1"><li 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Acids and bases </a></li><li><a href="../28031/topics-9-19-redox-process-1.html">Topics 9 & 19 : Redox process</a></li><li><a href="../28061/topics-10-20-organic-chemistry-1.html">Topics 10 & 20 : Organic chemistry</a></li><li><a href="../28038/topics-11-21-measurement-data-processing-analysis-1.html">Topics 11 & 21 : Measurement, data processing & analysis</a></li><li><a href="../28074/option-a-materials--1.html">Option A : Materials </a></li><li><a href="../28087/option-b-biochemistry-1.html">Option B : Biochemistry</a></li><li><a href="../28098/option-c-energy--1.html">Option C : Energy </a></li><li><a href="../28109/option-d-medicinal-chemistry-1.html">Option D : Medicinal chemistry</a></li></ul></li><li><a href="../41553/practical-work-including-ia-group-4-project--1.html" class="father">Practical work (including IA & Group 4 Project) </a><ul class="level-2"><li><a href="../41528/internal-assessment-1.html">Internal Assessment</a></li><li><a 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<nav id="sidemenu" class="side-nav"><div class="header"><span style="color: #fff;"><a href="../41465/complete-course-for-students--2.html">Complete course for students </a></span><span id="sidetreecontrol"><a title="Collapse all" rel="collapse" href="#"><i class="fa fa-minus-circle"></i></a> <a title="Expand all" rel="expand" href="#"><i class="fa fa-plus-circle"></i></a></span></div><ul class="level-0 always-expanded"><li class="ancestor parent" style="padding-left: 0px"><i class="expander fa fa-caret-right fa-rotate-90"></i><a href="../27988/full-coverage-of-each-topic-and-sub-topic-2.html" title="Full coverage of each topic and sub-topic">Full coverage of each topic and sub-topic</a></li><ul class="level-1 expanded"><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../27959/topic-1-stoichiometric-relationships-1.html" title="Topic 1 : Stoichiometric relationships">Topic 1 : Stoichiometric relationships</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27947/11-particulate-nature-of-matter-and-chemical-change--1.html" title="1.1 Particulate nature of matter and chemical change ">1.1 Particulate nature of matter and chemical change </a></li><li class=" parent" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27954/12-the-mole-concept-1.html" title="1.2 The mole concept">1.2 The mole concept</a></li><ul class="level-3 "><li class="" style="padding-left: 42px"><i class="expander fa fa-caret-right "></i><a href="../41469/comprehending-avogadros-constant-1.html" title="Comprehending Avogadro's constant">Comprehending Avogadro's constant</a></li></ul><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27958/13-reacting-masses-and-volumes--1.html" title="1.3 Reacting masses and volumes ">1.3 Reacting masses and volumes </a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../27960/topics-2-12-atomic-structure-1.html" title="Topics 2 & 12 : Atomic structure">Topics 2 & 12 : Atomic structure</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27961/21-the-nuclear-atom--1.html" title="2.1 The nuclear atom ">2.1 The nuclear atom </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27962/22-electron-configuration--1.html" title="2.2 Electron configuration ">2.2 Electron configuration </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27963/121-electrons-in-atoms--1.html" title="12.1 Electrons in atoms ">12.1 Electrons in atoms </a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../27965/topics-3-13-periodicity-1.html" title="Topics 3 & 13 : Periodicity">Topics 3 & 13 : Periodicity</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27966/31-the-periodic-table-1.html" title="3.1 The periodic table">3.1 The periodic table</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27967/32-periodic-trends--1.html" title="3.2 Periodic trends ">3.2 Periodic trends </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27968/131-first-row-d-block-elements-1.html" title="13.1 First-row d-block elements">13.1 First-row d-block elements</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27970/132-coloured-complexes-1.html" title="13.2 Coloured complexes">13.2 Coloured complexes</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../27971/topics-4-14-chemical-bonding-structure-1.html" title="Topics 4 & 14 : Chemical bonding & structure">Topics 4 & 14 : Chemical bonding & structure</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27972/41-ionic-bonding-structure--1.html" title="4.1 Ionic bonding & structure ">4.1 Ionic bonding & structure </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27973/42-covalent-bonding-1.html" title="4.2 Covalent bonding">4.2 Covalent bonding</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27974/43-covalent-structures-1--1.html" title="4.3 Covalent structures (1) ">4.3 Covalent structures (1) </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27980/43-covalent-structures-2--1.html" title="4.3 Covalent structures (2) ">4.3 Covalent structures (2) </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27981/44-intermolecular-forces--1.html" title="4.4 Intermolecular forces ">4.4 Intermolecular forces </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27982/45-metallic-bonding--1.html" title="4.5 Metallic bonding ">4.5 Metallic bonding </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27983/141-further-aspects-of-covalent-bonding-1.html" title="14.1 Further aspects of covalent bonding">14.1 Further aspects of covalent bonding</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27985/142-hybridization-1.html" title="14.2 Hybridization">14.2 Hybridization</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../27987/topics-5-15-energeticsthermochemistry-1.html" title="Topics 5 & 15 : Energetics/thermochemistry">Topics 5 & 15 : Energetics/thermochemistry</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27989/51-measuring-energy-changes-1.html" title="5.1 Measuring energy changes">5.1 Measuring energy changes</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27991/52-hesss-law-1.html" title="5.2 Hess's Law">5.2 Hess's Law</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27992/53-bond-enthalpies--1.html" title="5.3 Bond enthalpies ">5.3 Bond enthalpies </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27993/151-energy-cycles-1.html" title="15.1 Energy cycles">15.1 Energy cycles</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27994/152-entropy-spontaneity-1.html" title="15.2 Entropy & spontaneity">15.2 Entropy & spontaneity</a></li></ul><li class="ancestor parent" style="padding-left: 14px"><i class="expander fa fa-caret-right fa-rotate-90"></i><a href="../27995/topics-6-16-chemical-kinetics-1.html" title="Topics 6 & 16 : Chemical kinetics">Topics 6 & 16 : Chemical kinetics</a></li><ul class="level-2 expanded"><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27996/61-collision-theory-rates-of-reaction-1.html" title="6.1 Collision theory & rates of reaction">6.1 Collision theory & rates of reaction</a></li><li class="current" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="161-rate-expression-reaction-mechanism-1.html" title="16.1 Rate expression & reaction mechanism">16.1 Rate expression & reaction mechanism</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27998/162-activation-energy-1.html" title="16.2 Activation energy">16.2 Activation energy</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28001/topics-7-17-equilibrium--1.html" title="Topics 7 & 17 : Equilibrium ">Topics 7 & 17 : Equilibrium </a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../27999/71-equilibrium-1.html" title="7.1 Equilibrium">7.1 Equilibrium</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28000/171-equilibrium-law-1.html" title="17.1 Equilibrium law">17.1 Equilibrium law</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28017/topics-8-18-acids-and-bases--1.html" title="Topics 8 & 18 : Acids and bases ">Topics 8 & 18 : Acids and bases </a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28002/81-theories-of-acids-bases-1.html" title="8.1 Theories of acids & bases">8.1 Theories of acids & bases</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28010/82-properties-of-acids-bases-1.html" title="8.2 Properties of acids & bases">8.2 Properties of acids & bases</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28011/83-ph-scale-1.html" title="8.3 pH scale">8.3 pH scale</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28012/84-strong-weak-acids-bases-1.html" title="8.4 Strong & weak acids & bases">8.4 Strong & weak acids & bases</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28013/85-acid-deposition--1.html" title="8.5 Acid deposition ">8.5 Acid deposition </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28014/181-lewis-acids-bases--1.html" title="18.1 Lewis acids & bases ">18.1 Lewis acids & bases </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28015/182-calculations-involving-acids-bases--1.html" title="18.2 Calculations involving acids & bases ">18.2 Calculations involving acids & bases </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28016/183-ph-titration-curves-1.html" title="18.3 pH titration curves">18.3 pH titration curves</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28031/topics-9-19-redox-process-1.html" title="Topics 9 & 19 : Redox process">Topics 9 & 19 : Redox process</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28021/91-oxidation-reduction-1.html" title="9.1 Oxidation & reduction">9.1 Oxidation & reduction</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28022/92-electrochemical-cells-1.html" title="9.2 Electrochemical cells">9.2 Electrochemical cells</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28023/191-electrochemical-cells-ahl-1.html" title="19.1 Electrochemical cells (AHL)">19.1 Electrochemical cells (AHL)</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28061/topics-10-20-organic-chemistry-1.html" title="Topics 10 & 20 : Organic chemistry">Topics 10 & 20 : Organic chemistry</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28042/101-fundamentals-of-organic-chemistry-1.html" title="10.1 Fundamentals of organic chemistry">10.1 Fundamentals of organic chemistry</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28043/1021-alkanes-alkenes-addition-polymers-1.html" title="10.2(1) Alkanes, alkenes & addition polymers">10.2(1) Alkanes, alkenes & addition polymers</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28044/1022-alcohols--1.html" title="10.2(2) Alcohols ">10.2(2) Alcohols </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28047/1023-halogenoalkanes-benzene-1.html" title="10.2(3) Halogenoalkanes & benzene">10.2(3) Halogenoalkanes & benzene</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28050/2011-nucleophilic-substitution--1.html" title="20.1(1) Nucleophilic substitution ">20.1(1) Nucleophilic substitution </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28051/2012-electrophilic-addition--1.html" title="20.1(2) Electrophilic addition ">20.1(2) Electrophilic addition </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28053/2013-electrophilic-substitution-1.html" title="20.1(3) Electrophilic substitution">20.1(3) Electrophilic substitution</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28054/2014-reduction-reactions--1.html" title="20.1(4) Reduction reactions ">20.1(4) Reduction reactions </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28056/202-synthetic-routes--1.html" title="20.2 Synthetic routes ">20.2 Synthetic routes </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28059/203-stereoisomerism--1.html" title="20.3 Stereoisomerism ">20.3 Stereoisomerism </a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28038/topics-11-21-measurement-data-processing-analysis-1.html" title="Topics 11 & 21 : Measurement, data processing & analysis">Topics 11 & 21 : Measurement, data processing & analysis</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28032/111-uncertainty-errors--1.html" title="11.1 Uncertainty & errors ">11.1 Uncertainty & errors </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28033/112-graphical-techniques-1.html" title="11.2 Graphical techniques">11.2 Graphical techniques</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28034/113-spectroscopic-identification-of-organic-compounds-1.html" title="11.3 Spectroscopic identification of organic compounds">11.3 Spectroscopic identification of organic compounds</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28039/211-spectroscopic-identification-of-organic-compounds-ahl-1.html" title="21.1 Spectroscopic identification of organic compounds (AHL)">21.1 Spectroscopic identification of organic compounds (AHL)</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28074/option-a-materials--1.html" title="Option A : Materials ">Option A : Materials </a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28062/a1-introduction-to-materials-science--1.html" title="A.1 Introduction to materials science ">A.1 Introduction to materials science </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28063/a2-metals-and-icp-spectroscopy-1.html" title="A.2 Metals and ICP spectroscopy">A.2 Metals and ICP spectroscopy</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28065/a3-catalysts--1.html" title="A.3 Catalysts ">A.3 Catalysts </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28066/a4-liquid-crystals-1.html" title="A.4 Liquid crystals">A.4 Liquid crystals</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28067/a5-polymers-1.html" title="A.5 Polymers">A.5 Polymers</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28069/a6-nanotechnology-1.html" title="A.6 Nanotechnology">A.6 Nanotechnology</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28070/a7-environmental-impact-plastics-1.html" title="A.7 Environmental impact - plastics">A.7 Environmental impact - plastics</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28071/a8-superconducting-metals-x-ray-crystallography--1.html" title="A.8 Superconducting metals & X-ray crystallography ">A.8 Superconducting metals & X-ray crystallography </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28072/a9-condensation-polymers-1.html" title="A.9 Condensation polymers">A.9 Condensation polymers</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28073/a10-environmental-impact-heavy-metals-1.html" title="A.10 Environmental impact - heavy metals">A.10 Environmental impact - heavy metals</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28087/option-b-biochemistry-1.html" title="Option B : Biochemistry">Option B : Biochemistry</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28076/b1-introduction-to-biochemistry--1.html" title="B.1 Introduction to biochemistry ">B.1 Introduction to biochemistry </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28078/b2-proteins-enzymes-1.html" title="B.2 Proteins & enzymes">B.2 Proteins & enzymes</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28079/b3-lipids-1.html" title="B.3 Lipids">B.3 Lipids</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28080/b4-carbohydrates-1.html" title="B.4 Carbohydrates">B.4 Carbohydrates</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28081/b5-vitamins-1.html" title="B.5 Vitamins">B.5 Vitamins</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28082/b6-biochemistry-the-environment-1.html" title="B.6 Biochemistry & the environment">B.6 Biochemistry & the environment</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28083/b7-proteins-enzymes-ahl--1.html" title="B.7 Proteins & enzymes (AHL) ">B.7 Proteins & enzymes (AHL) </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28084/b8-nucleic-acids-1.html" title="B.8 Nucleic acids">B.8 Nucleic acids</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28085/b9-biological-pigments-1.html" title="B.9 Biological pigments">B.9 Biological pigments</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28086/b10-stereochemistry-in-biomolecules-1.html" title="B.10 Stereochemistry in biomolecules">B.10 Stereochemistry in biomolecules</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28098/option-c-energy--1.html" title="Option C : Energy ">Option C : Energy </a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28088/c1-energy-sources--1.html" title="C.1 Energy sources ">C.1 Energy sources </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28089/c2-fossil-fuels-1.html" title="C.2 Fossil fuels">C.2 Fossil fuels</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28090/c3-nuclear-fusion-nuclear-fission-reactions-1.html" title="C.3 Nuclear fusion & nuclear fission reactions">C.3 Nuclear fusion & nuclear fission reactions</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28091/c4-solar-energy--1.html" title="C.4 Solar energy ">C.4 Solar energy </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28094/c5-environmental-impact-global-warming--1.html" title="C.5 Environmental impact - global warming ">C.5 Environmental impact - global warming </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28095/c6-electrochemistry-rechargeable-batteries-fuel-cells-1.html" title="C.6 Electrochemistry, rechargeable batteries & fuel cells">C.6 Electrochemistry, rechargeable batteries & fuel cells</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28096/c7-nuclear-fusion-fission-hl--1.html" title="C.7 Nuclear fusion & fission (HL) ">C.7 Nuclear fusion & fission (HL) </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28097/c8-photovoltaic-cells-and-dsscs-1.html" title="C.8 Photovoltaic cells and DSSCs">C.8 Photovoltaic cells and DSSCs</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../28109/option-d-medicinal-chemistry-1.html" title="Option D : Medicinal chemistry">Option D : Medicinal chemistry</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28099/d1-pharmaceutical-products-drug-action--1.html" title="D.1 Pharmaceutical products & drug action ">D.1 Pharmaceutical products & drug action </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28100/d2-aspirin-penicillin-1.html" title="D.2 Aspirin & penicillin">D.2 Aspirin & penicillin</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28101/d3-opiates-1.html" title="D.3 Opiates">D.3 Opiates</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28103/d4-ph-regulation-of-the-stomach-1.html" title="D.4 pH regulation of the stomach">D.4 pH regulation of the stomach</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28102/d5-antiviral-medications-1.html" title="D.5 Antiviral medications">D.5 Antiviral medications</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28104/d6-environmental-impact-of-some-medications-1.html" title="D.6 Environmental impact of some medications">D.6 Environmental impact of some medications</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28105/d7-taxol-a-chiral-auxiliary-case-study--1.html" title="D.7 Taxol - a chiral auxiliary case study ">D.7 Taxol - a chiral auxiliary case study </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28107/d8-nuclear-medicine--1.html" title="D.8 Nuclear medicine ">D.8 Nuclear medicine </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../28108/d9-drug-detection-analysis-1.html" title="D.9 Drug detection & analysis">D.9 Drug 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</div><section id="main-content"><div id="toc-1672969232" class="toc"><a href="#" class="toc-switcher" title="Show table of contents"><small><i class="fa fa-reorder"></i> Table of contents <span class="pull-right"><i class="fa fa-chevron-down"></i></span></small></a></div><p>Written specifically for students to provide help and support for the IB Diploma chemistry <span data-scayt-word="programme" data-wsc-lang="en_US">programme</span> this page provides full coverage of the syllabus content of Topic 6.2 Rate expression & reaction mechanism. It encourages you to think critically and provides many questions with full worked answers so that you can monitor and improve your knowledge and understanding.</p><div class="box"><h2><img alt="" src="../../../ib/chemistry/images/student-learning/reaction-pathway-for-rds(1).png" style="width: 2px; height: 1px;"><img alt="" height="21" src="../../../img/tib-icons/higher-level-32-1.png" title="" width="21"> Learning outcomes</h2><p><img alt="" class="noborder" src="../../../ib/chemistry/images/student-learning/reaction-pathway-for-rds(1).png" style="float: right; width: 450px; height: 317px;">After studying this topic you should be able to:</p><p><strong><strong>Understand</strong></strong></p><ul><li>Reactions may involve more than one step and the slowest step determines the rate of reaction (This step is known as the rate determining step, RDS.</li><li>The number of reactant particles taking part in any specified step is known as the molecularity.</li><li>The order of a reaction can be either an integer or fractional. The order of a reaction can describe, with respect to a reactant, the number of particles<br>taking part in the rate-determining step.</li><li>All rate equations can only be determined by experiment.</li><li>The units of a rate constant are determined by the overall order of the reaction and the value of the rate constant, <em>k</em>, is affected by temperature.</li><li>Catalysts alter a reaction mechanism by producing a step with a lower activation energy.</li></ul><p><strong>Apply your knowledge to:</strong></p><ul><li>Deduce the rate expression for an equation from experimental data and solve problems involving the rate expression.</li><li>Sketch, identify, and analyse graphical representations for zero, first and second order reactions.</li><li>Evaluate proposed reaction mechanisms to show they are (or are not) consistent with kinetic and<br>stoichiometric data.<hr class="hidden"></li></ul></div><hr class="hidden"><div class="blueBg"><h2>Relationships & vocabulary</h2><h4>Nature of science</h4><p>Rather like <a href="../27996/61-collision-theory-rates-of-reaction-1.html" title="6.1 Collision theory & rates of reaction">6.1 Collision theory & rates of reaction</a>, this sub-topic also provides a good example of the Principle of Occam’s razor. As theories develop they need to remain as simple as possible while maximizing their powers of explanation. Because the probability of collisions between three reacting species is low it means that stepwise reaction mechanisms are more likely.</p><hr class="hidden"><h4>International-mindedness</h4><p>The first industrial catalyst to be used was for the Contact process to produce sulfuric acid. It has been stated that for a long time the amount of sulfuric acid produced by a country closely mirrored the country’s economic health. What are some of the current indicators for a country’s economic health?</p><hr class="hidden"><p>For more examples and links to <em>International mindedness, Theory of knowledge, utilization etc. </em>see <a href="../17854/topics-6-16--1.html" title="Core & AHL » Incorporating IM, TOK, 'Utilization' etc. » Topics 4 & 14 ">separate page</a> which covers all of Topics 6 & 16: Chemical kinetics.</p><hr class="hidden"><h4>Vocabulary</h4><table><tbody><tr><td>rate constant, <em>k</em></td><td>rate expression</td><td>rate equation</td><td>order of reaction</td><td>overall order</td></tr><tr><td>half-life, t<sub>½</sub></td><td>slow step</td><td>fast step</td><td>rate-determining step</td><td>reaction mechanism</td></tr></tbody></table><hr class="hidden"></div><hr class="hidden"><div class="greenBg"><h2 id="header-6">Learning slides</h2><p>You can use this slide gallery for learning or for reviewing concepts and information. It covers all the key points in the syllabus for this sub-topic.</p><div id="myCarousel-14" class="carousel slide" data-id="270"><!-- Carousel items --><div class="carousel-inner"><div class="active item"><a class="fancy" href="../../../tib-galleries/3-270/1611.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1611.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/1622.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1622.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/1613.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1613.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/1614.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1614.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/1615.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1615.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/1616.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1616.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/1617.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1617.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/1618.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1618.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/1619.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/1619.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="/files/tib-galleries/3-270/slide.png" rel="gallery-270" title=""><img alt="" src="/files/tib-galleries/3-270/slide.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/16111.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/16111.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="/files/tib-galleries/3-270/corrected-slide-1.png" rel="gallery-270" title=""><img alt="" src="/files/tib-galleries/3-270/corrected-slide-1.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/16113.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/16113.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="/files/tib-galleries/3-270/edited-.png" rel="gallery-270" title=""><img alt="" src="/files/tib-galleries/3-270/edited-.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-270/16115.png" rel="gallery-270" title=""><img alt="" src="files/tib-galleries/3-270/16115.png"></a><div class="carousel-caption"><p>Rate expression & reaction mechanism: </p></div></div></div><!-- Carousel nav --><a class="carousel-control left" href="#myCarousel-14" data-slide="prev">‹</a><a class="carousel-control right" href="#myCarousel-14" data-slide="next">›</a><div class="tib-indicators"><img class="" title="Click to view" style="margin: 10px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1611-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1622-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1613-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1614-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1615-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1616-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1617-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1618-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/1619-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="/files/tib-galleries/3-270/slide-thumb128.png"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/16111-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="/files/tib-galleries/3-270/corrected-slide-1-thumb128.png"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/16113-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="/files/tib-galleries/3-270/edited--thumb128.png"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-270/16115-thumb128.jpg"></div></div><p> </p></div><hr class="hidden"><div class="pinkBg"><div><h2>Something to think about</h2><p><strong>1.</strong> While I was searching around on the Internet I came across <a href="../../../HH015.doc">a worksheet</a> with questions on the rate expression.</p><p>The first two questions are:</p><p>1) Write the following for the reaction N<sub>2</sub> + 3H<sub>2</sub> → 2NH<sub>3</sub></p><p>(a) The rate expression for the reaction</p><p>(b) The order of the reaction in each of the reagents</p><p>(c) The overall order of the reaction</p><p>2) The rate constant for the reaction HNO<sub>3</sub> + NH<sub>3</sub> → NH<sub>4</sub>NO<sub>3</sub> is 14.5 L / mol.sec.<br>If the concentration of nitric acid is 0.050 M and the concentration of ammonia is 0.10 M, what will the rate of this reaction be?</p><p>The answers are then given:</p><p>1).<br>(a) Rate = k[N<sub>2</sub>][H<sub>2</sub>]<sup>3</sup></p><p>(b) The reaction is first order in nitrogen and third order in hydrogen.</p><p>(c) The overall order of the reaction is fourth order</p><p>2). Rate = k[HNO<sub>3</sub>][NH<sub>3</sub>]</p><p>Rate = (14.5 L / mol.sec)(0.050 M)(0.10 M)</p><p>Rate = 0.073 mol / L. sec</p><p>The question uses M and L /mol. sec whereas we use mol dm<sup>-3</sup> and dm<sup>-3</sup> mol <sup>-1</sup> s<sup>-1</sup> and no states are given and <em>k</em> is not in italics but all that is only a question of convention. What is completely wrong is that these questions are unanswerable with the information given. Rate expressions <strong>cannot be determined from the stoichiometric equation</strong>. They can only be arrived at from experimental data.</p><p>The rate equation for the first question can only be expressed as:</p><p>rate = <em>k</em>[N<sub>2</sub>]<em><sup>x</sup></em>[H<sub>2</sub>]<em><sup>y </sup></em></p><p>where<sup> </sup> <em>x</em> and <em>y</em> are the order of the reaction with respect to nitrogen and hydrogen and must be found by experiment.</p><hr class="hidden"><img alt="" class="right noborder" src="../../../ib/chemistry/images/Core%20and%20AHL/Kinetics/Habers%20apparatus.jpg" style="width: 315px; height: 255px;" title="The apparatus devised by Fritz Haber to synthesise ammonia from nitrogen and hydrogen"><p>In fact work by <a href="http://www.sciencedirect.com/science/article/pii/0021951777902378">Ertl and others</a> have shown that in the Haber Process (right) where an iron catalyst is used the reaction is complex and thought to proceed by the following steps:</p><ol><li>N<sub>2</sub> (g) → N<sub>2</sub> (adsorbed)</li><li>N<sub>2</sub> (adsorbed) → 2 N (adsorbed)</li><li>H<sub>2</sub>(g) → H<sub>2</sub> (adsorbed)</li><li>H<sub>2</sub> (adsorbed) → 2 H (adsorbed)</li><li>N (adsorbed) + 3 H(adsorbed)→ NH<sub>3</sub> (adsorbed)</li><li>NH<sub>3</sub> (adsorbed) → NH<sub>3</sub> (g)</li></ol><p>The second step is the slowest step which suggests that [H<sub>2</sub>] does not even appear in the rate equation.</p><hr class="hidden"><p>Another example to illustrate the same point is the reaction of hydrogen with halogens:</p><p>H<sub>2</sub>(g) + X<sub>2</sub>(g) → 2HX(g)</p><p>When X is iodine, the experimentally determined rate expression looks as if it could be deduced from the stoichiometric equation as it is:</p><p>rate = <em>k</em>[H<sub>2</sub>(g)][l<sub>2</sub>(g)]</p><p>but it is very different case when bromine is involved</p><p>rate = <em>k</em>[H<sub>2</sub>(g)][Br<sub>2</sub>(g)]<sup>½</sup> / ([Br<sub>2</sub>(g)] + <em>k</em>'[HBr(g)]</p><hr class="hidden"><p><strong>2.</strong> Just a question concerning reaction mechanisms that a student of mine once asked which you might like to reflect upon.</p><p>We were looking at nucleophilic substitution reactions and specifically why the hydroxide ion is a better nucleophile than water. During the discussion I confirmed the answer given by most of the students that the hydroxide ion is more electron rich and therefore it will be attracted more strongly to the δ+ carbon atom of the halogenoalkane. Her question was: How can we know that hydroxide ions are better nucleophiles than water in the case of tertiary halogenoalkanes? She argued that when the halogenoalkane is tertiary the first step in the reaction is the dissociation of the halogenoalkane into the halogen ion and the tertiary carbocation. Since this is a first order reaction with the rate only depending upon the concentration of the halogenoalkane the first step is the slow step in the reaction. Therefore the nucleophile will play no part in the overall rate and so there should be no difference in the rate when either water or hydroxide ions are used as the nucleophile.</p><p>S<sub>N</sub>2 mechanism. The better nucleophile should give a faster rate as both the nucleophile and the halogenoalkane are involved in the rate determining step:</p><p style="text-align: center;"><img alt="" class="noborder" height="115" src="../../../ib/chemistry/images/Core%20and%20AHL/Kinetics/SN2%20mechanism%20.jpg" title="SN2 mechanism" width="682"></p><p>S<sub>N</sub>1 mechanism. The first step is the slow step with only the halogenoalkane involved:</p><p style="text-align: center;"><img alt="" class="noborder" height="126" src="../../../ib/chemistry/images/Core%20and%20AHL/Kinetics/SN1%20mechanism.jpg" title="First step of SN1 mechanism - the slow step" width="607"></p><p>Since the second step is faster the nature of the nucleophile should make no difference to the overall rate of the reaction so it is impossible to determine which is the better nucleophile in this situation:</p><p style="text-align: center;"><img alt="" class="noborder" height="145" src="../../../ib/chemistry/images/Core%20and%20AHL/Kinetics/SN1%20mechanism1.jpg" title="Th esecond step of an SN1 mechanism - the faster step" width="529"></p><p>She was a smart student!</p><hr class="hidden"></div></div><hr class="hidden"><div class="yellowBg"><h2 id="header-8">Test your understanding of this topic</h2><p><em>(Note that your teacher may have restricted your access to some or all of these questions and worked answers if they are going to use them as a class test or set them as an assignment.)</em></p><hr class="hidden"><p>For ten 'quiz' multiple choice questions with the answers explained see <a href="../24645/mctest-rate-expression-reaction-mechanisms.html" title="Core & AHL » Teaching each topic & sub-topic » Topics 6 & 16 » Rate expression & reaction mechanism » MCTest: Rate expression & reaction mechanisms">MCTest: Rate expression & reaction mechanisms</a>.</p><p>For short-answer questions on rate expressions see <a href="../40949/rate-expression-questions-1.html" title="Core & AHL » Teaching each topic & sub-topic » Topics 6 & 16 » Rate expression & reaction mechanism » Rate expression questions">Rate expression questions</a>.</p><p>For short-answer questions on reaction mechanisms see <a href="../40950/reaction-mechanisms-questions-1.html" title="Core & AHL » Teaching each topic & sub-topic » Topics 6 & 16 » Rate expression & reaction mechanism » Reaction mechanisms questions">Reaction mechanisms questions</a>.</p><hr class="hidden"></div><hr class="hidden"><div class="blueBg"><h2><span style="font-weight: bold;">More resources</span></h2><p><strong>1. </strong>Deducing the rate expression by looking at initial rates by Richard Thornley, an IB teacher at the International School of Genoa. The video also looks at the units of the rate constant, <em>k, </em>although this is explained more in the next video.</p><p style="text-align: center;"><iframe allowfullscreen="" frameborder="0" height="280" src="//www.youtube.com/embed/YLB732ij2oI?rel=0" width="360"></iframe></p><p style="text-align: center;"><a href="http://youtu.be/YLB732ij2oI">Rate expression <img src="http://www.thinkib.net/img/icons/video.png"></a></p><hr class="hidden"><p><strong>2. </strong>Another Richard Thornley video - this time on order or reaction and rate constants.</p><p style="text-align: center;"><iframe allowfullscreen="" frameborder="0" height="280" src="//www.youtube.com/embed/9sMFJMuZzmg?rel=0" width="360"></iframe></p><p style="text-align: center;"><a href="http://youtu.be/9sMFJMuZzmg">Order of reaction <img src="http://www.thinkib.net/img/icons/video.png"></a></p><hr class="hidden"><p><strong>3</strong>. A nice visual demonstration by Richard Thornley showing the importance of the rate determining step.</p><p style="text-align: center;"><iframe allowfullscreen="" frameborder="0" height="280" src="//www.youtube.com/embed/swnJeRo-u8Q?rel=0" width="360"></iframe></p><p style="text-align: center;"><a href="http://youtu.be/swnJeRo-u8Q">Rate determining step <img class="ico" src="../../../img/icons/video-1.png"><span class="anchor" id="video-1" name="video-1"> </span></a></p><hr class="hidden"><p><strong>4. </strong>There are a lot of 'lecture' type video clips on YouTube on reaction mechanisms. Here is one by Mark Rosengarten.</p><p style="text-align: center;"><iframe allowfullscreen="" frameborder="0" height="280" src="//www.youtube.com/embed/-ctr9MUM_hI?rel=0" width="360"></iframe></p><p style="text-align: center;"><a href="http://youtu.be/-ctr9MUM_hI">Reaction mechanism <img class="ico" src="../../../img/icons/video-1.png"><span class="anchor" id="video-2" name="video-2"> </span></a></p><hr class="hidden"><p style="text-align: center;"></p></div></section></article><section id="media-extras"><div class="page-actions no-print navbar inline hidden-desktop"><div class="navbar-inner"><ul class="nav"><li><a class="presentation" href="#" onclick="return false;"><i class="fa fa-desktop"></i></a></li><li><a class="print-section-blog" href="#" onclick="return false;"><i class="fa fa-print"></i></a></li><li><a class="page-bookmarker" data-ticket="IB Docs (2) Team" data-pid="27997" href="#" onclick="return false;"><i class="fa fa-star"></i></a></li><li><a class="personal-notes" href="#" onclick="return false;"><i class="fa fa-file-text"></i></a></li><li><a class="" data-toggle="modal" href="#modal-feedback" onclick="return false;"><i class="fa fa-envelope-o"></i></a></li><li class="dropdown"><a class="dropdown-toggle" data-toggle="dropdown" data-target="#" href="#"><i class="fa fa-share-alt"></i></a><ul class="dropdown-menu" role="menu"><li><a class="" target="_blank" title="Share on Twitter" href="https://twitter.com/share?text=%2216.1+Rate+expression+%26+reaction+mechanism%22+-+via+%40InThinker+%23chemistry%0A&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F27997%2F161-rate-expression-reaction-mechanism"><i class="fa fa-twitter-square"></i><span>Twitter</span></a></li><li><a class="" target="_blank" title="Share on Facebook" href="https://www.facebook.com/sharer.php?u=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F27997%2F161-rate-expression-reaction-mechanism&t=16.1+Rate+expression+&+reaction+mechanism"><i class="fa fa-facebook-square"></i><span>Facebook</span></a></li><li><a class="" href="http://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F27997%2F161-rate-expression-reaction-mechanism"><i class="fa fa-linkedin-square"></i><span>LinkedIn</span></a></li><li><a class="" href="https://plus.google.com/share?url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F27997%2F161-rate-expression-reaction-mechanism"><i class="fa fa-google-plus-square"></i><span>Google +</span></a></li><li><a class="" href="mailto:?subject=16.1 Rate expression & reaction mechanism&body=Written specifically for students to provide help and support for the IB Diploma chemistry programme this page provides full coverage of the syllabus content of Topic 6.2 Rate expression & reaction mechanism. 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<h3><i class="fa fa-file colored"></i> 16.1 Rate expression & reaction mechanism</h3>
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