{"id":10710,"date":"2026-09-26T13:54:27","date_gmt":"2026-09-26T12:54:27","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/measuring-and-calculating-rates\/"},"modified":"2026-10-04T23:03:14","modified_gmt":"2026-10-04T22:03:14","slug":"measuring-and-calculating-rates","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/measuring-and-calculating-rates\/","title":{"rendered":"Measuring and Calculating Rates"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-kinetics-equilibria-page\">\n  <style>\n    .ols-revision-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --soft-blue: #eef4ff;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-green: #f0f7f1;\n      --gold: #c9973a;\n      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20px;\n      box-shadow: var(--inner-shadow);\n    }\n.ols-faq-item h3 {\n      margin: 0 0 8px;\n      font-size: 20px;\n      line-height: 1.3;\n      color: var(--navy);\n    }\n.ols-faq-item p {\n      margin: 0;\n      font-size: 16px;\n      line-height: 1.65;\n      color: var(--body-text);\n    }\n.ols-faq-card,\n      .ols-quicksnap-card,\n      .ols-attribution-card {\n        padding: 24px 18px;\n        border-radius: 22px;\n      }\n  <\/style>\n\n    <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>A Level Chemistry<\/p>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Topic 9 Kinetics &amp; Equilibria<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/\">Topic 9 Overview<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/\">Topic 9A Kinetics<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/collision-theory-and-rates-of-reaction\/\">Collision Theory and Rates of Reaction<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/measuring-and-calculating-rates\/\">Measuring and Calculating Rates<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/maxwell-boltzmann-distribution\/\">The Maxwell\u2013Boltzmann Distribution<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/catalysts-and-reaction-profiles\/\">Catalysts and Reaction Profiles<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-9a-9b-iodine-propanone-and-clock-reaction-kinetics\/\">Core Practical 9A\/9B<\/a>\n          <\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9b-equilibria\/\">Topic 9B Equilibria<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9b-equilibria\/dynamic-equilibrium\/\">Dynamic Equilibrium<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9b-equilibria\/le-chateliers-principle\/\">Le Chatelier's Principle<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9b-equilibria\/equilibria-in-industry\/\">Equilibria in Industry<\/a>\n          <\/li>\n        <\/ul>\n      <\/li>\n    <\/ul>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Other Topics<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-6-energetics\/\">Topic 6 Energetics<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-7-intermolecular-forces\/\">Topic 7 Intermolecular Forces<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-8-redox-chemistry-and-groups-1-2-and-7\/\">Topic 8 Redox &amp; Groups 1, 2 and 7<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/\">Core Practicals<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n<\/aside>\n\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, .active-main, .parent-active').forEach(function(item) {\r\n      item.classList.remove('active', 'active-main', 'parent-active');\r\n    });\r\n\r\n    sidebar.querySelectorAll('a[data-ols-disabled-parent=\"1\"], a[aria-current]').forEach(function(a) {\r\n      a.removeAttribute('aria-current');\r\n      a.removeAttribute('tabindex');\r\n      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}\r\n})();\r\n<\/script>\r\n\n\n    <main class=\"ols-main\">\n\n      <!-- BREADCRUMBS - updated with full path and correct links -->\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Edexcel International<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/\">Topic 9 Kinetics and Equilibria<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/\">Topic 9A Kinetics<\/a> \/\n<span>Measuring and Calculating Rates<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Measuring and Calculating Rates<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to following a reaction by mass loss, gas volume or time, rate from 1 \u00f7 time in clock reactions, and rate from the gradient of a tangent to a concentration\u2013time curve, with the units of rate.<\/p>\n        <div class=\"ols-badges\">\n<div class=\"ols-badge\">Exam board: Edexcel International<\/div>\n<div class=\"ols-badge\">Unit 2: WCH12\/01<\/div>\n<div class=\"ols-badge\">Topic 9A Kinetics<\/div>\n<\/div>\n        <div class=\"ols-author\">\n\n    <img decoding=\"async\"\n      class=\"ols-author-avatar-img\"\n      src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n      alt=\"Dr. Mohammed Al-Fatah\"\n    >\n\n    <div class=\"ols-author-content\">\n\n      <h2 class=\"ols-author-title\">\n        Written by: Dr. Mohammed Al-Fatah\n      <\/h2>\n\n      <p class=\"ols-author-description\">\n        Chemistry specialist revision notes for A Level Chemistry.\n      <\/p>\n\n      <a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" target=\"_blank\" rel=\"noopener noreferrer\">\n        <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n          <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"\/>\n        <\/svg>\n        View LinkedIn Profile\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>Following a Reaction<\/h2>\n<\/div>\n<p>To measure a rate, something that changes as the reaction happens has to be followed over time. Which quantity is chosen depends on the reaction.<\/p><p>If a gas is given off, the <strong>loss in mass<\/strong> of the flask on a balance, or the <strong>volume of gas<\/strong> collected in a gas syringe, can be recorded every few seconds.<\/p><p>If a colour appears or disappears, the change can be timed or followed with a colorimeter. If a solid precipitate forms, the <strong>time for a cross to disappear<\/strong> under the flask gives a simple measure.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Method<\/th><th>What is measured<\/th><th>Suitable for<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Mass loss<\/strong><\/td><td>Mass of flask and contents on a balance against time, with cotton wool in the neck to let the gas out<\/td><td>Reactions giving off a dense gas such as CO\u2082 (marble chips and acid)<\/td><\/tr>\n<tr><td><strong>Gas volume<\/strong><\/td><td>Volume in a gas syringe or an inverted burette against time<\/td><td>Any gas, including H\u2082 (magnesium and acid) and O\u2082 (decomposition of hydrogen peroxide)<\/td><\/tr>\n<tr><td><strong>Time for a change<\/strong><\/td><td>Time until a cross under the flask disappears, or until a colour appears<\/td><td>Precipitation of sulfur from sodium thiosulfate and acid; iodine clock reactions<\/td><\/tr>\n<tr><td><strong>Colour<\/strong><\/td><td>Absorbance in a colorimeter, or titrating samples that have been quenched<\/td><td>Iodine and propanone; reactions of coloured ions<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>A <strong>clock reaction<\/strong> is one where a sudden change, such as the appearance of a blue-black iodine\u2013starch colour, marks the point when a fixed amount of product has formed. Because the same amount of product forms each time, the rate is proportional to 1 \u00f7 time.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Whatever is followed, the rate at any moment is how fast that quantity is changing at that moment.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>Rate from a Time: rate = 1 \u00f7 t<\/h2>\n<\/div>\n<p>When the same amount of reaction is timed under different conditions, the <strong>average rate<\/strong> is proportional to <strong>1 \u00f7 time<\/strong>.<\/p><p>In the sodium thiosulfate and hydrochloric acid reaction, Na\u2082S\u2082O\u2083 + 2HCl \u2192 2NaCl + SO\u2082 + S + H\u2082O, the sulfur makes the mixture cloudy and the cross disappears when a fixed amount of sulfur has formed.<\/p><p>If the cross disappears in 40 s at one concentration and 20 s at double the concentration, the rate has doubled, because 1\/20 is twice 1\/40.<\/p>\n<p>Plotting 1\/t against concentration (or temperature) shows how the rate depends on that condition. This is an approximation, because 1\/t does not have the units of a true rate, but it is exactly what is needed to compare runs.<\/p>\n<p>The two halves of <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-9a-9b-iodine-propanone-and-clock-reaction-kinetics\/\">Core Practical 9A\/9B (iodine\u2013propanone and clock reactions)<\/a> use both approaches: the iodine\u2013propanone reaction is followed by quenching and titrating samples, and the clock reaction gives rate from 1\/t.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Worked example:<\/strong> A clock reaction takes 84 s at 20 \u00b0C and 42 s at 30 \u00b0C. Rate \u221d 1\/t, so the rate at 30 \u00b0C is (1\/42) \u00f7 (1\/84) = 2 times the rate at 20 \u00b0C: the usual &#8220;doubling for 10 \u00b0C&#8221;.<\/p>\n<\/div>\n<div class=\"ols-figure-card ols-zoom-pop\">\n<div class=\"ols-figure-image\">\n<a class=\"ols-image-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/t9x-clockrate.jpg\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open image fullscreen\">\n<img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/t9x-clockrate.jpg\" alt=\"Worked cards using 1 \u00f7 time to compare rates for concentration and temperature changes, with a sketch of 1\/t against concentration.\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/t9x-clockrate.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>Because every run is timed to the same amount of product, 1 \u00f7 time compares the rates directly: halving the time doubles the rate.<\/p><\/div>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Check: Rate from Time<\/h2>\n<p>Use rate \u221d 1\/t on results that are not the ones above.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"902\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>Rate from a Graph: the Gradient<\/h2>\n<\/div>\n<p>When concentration (or volume, or mass) is plotted against time, the <strong>gradient<\/strong> of the curve at any point is the rate at that time.<\/p><p>The curve is steepest at the start, because the reactants are most concentrated, and flattens as they are used up until the gradient is zero and the reaction has finished.<\/p>\n<p>To find the rate at a particular time, draw a <strong>tangent<\/strong> to the curve at that time and calculate its gradient: the change in the y quantity divided by the change in time over the length of the tangent.<\/p><p>The <strong>initial rate<\/strong> is the gradient of the tangent at t = 0, which is the largest value.<\/p><p>If concentration is on the y-axis the gradient has units of mol dm\u207b\u00b3 s\u207b\u00b9; if gas volume is on it, cm\u00b3 s\u207b\u00b9.<\/p>\n<p>Two curves for the same reaction under different conditions can be compared by their initial gradients. The same amount of reactant always gives the same final amount of product, so the curves level off at the same height, but the faster reaction gets there sooner.<\/p>\n<div class=\"ols-figure-card ols-zoom-pop\">\n<div class=\"ols-figure-image\">\n<a class=\"ols-image-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/kinetics-equilibria-measuring-rates.jpg\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open image fullscreen\">\n<img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/kinetics-equilibria-measuring-rates.jpg\" alt=\"Three ways to follow a rate, and a concentration\u2013time graph with tangents giving the initial rate and the rate at time t\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/kinetics-equilibria-measuring-rates.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>Three ways of following a reaction, and how the tangent to a concentration\u2013time curve gives the initial rate and the rate at a later time.<\/p><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> Draw the tangent with a ruler so that it touches the curve at one point only, make it long, and show the triangle you used for the gradient. A tangent at t = 0 gives the initial rate.<\/p>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Check: Gradients and Curves<\/h2>\n<p>Interpret rate graphs for reactions that are not on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"903\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>Common Exam Points<\/h2>\n<\/div>\n<h3>Say<\/h3><p>&#8220;Rate = gradient of the tangent to the curve at that time.&#8221; &#8220;The initial rate is the gradient at t = 0.&#8221; &#8220;The curve levels off because the limiting reactant has been used up.&#8221;<\/p>\n<h3>Do not say<\/h3><p>&#8220;The rate is the gradient of the line joining the start and the end&#8221; (that is an average rate, not the rate at a time). Do not read a gradient from a curve without drawing a tangent.<\/p>\n<h3>Watch for<\/h3><p>Units: check what is on the y-axis before writing the unit of the rate. A volume\u2013time graph gives cm\u00b3 s\u207b\u00b9, a concentration\u2013time graph gives mol dm\u207b\u00b3 s\u207b\u00b9.<\/p>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Check: Units and Comparisons<\/h2>\n<p>Quick questions on the units of rate and on comparing two curves.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-904\" class=\"h5p-iframe\" data-content-id=\"904\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Kinetics and Equilibria Quick Choice: Units and Comparisons\"><\/iframe><\/div><\/div>\n<\/section>\n<section class=\"ols-faq-card\">\n<h2>FAQs<\/h2>\n<p>Use these quick answers to check the measuring and graph skills.<\/p>\n\n<div class=\"ols-faq-list\">\n<div class=\"ols-faq-item\">\n<h3>Why is rate = 1\/t only an approximation?<\/h3>\n<p>Because it measures the average rate over the time taken to form a fixed amount of product, and it has units of s\u207b\u00b9 rather than mol dm\u207b\u00b3 s\u207b\u00b9. It is fine for comparing runs where the same amount of product forms.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Where is the reaction fastest on a concentration\u2013time graph?<\/h3>\n<p>At the start, where the curve is steepest, because the reactant concentration is highest. The gradient falls as the reactant is used up.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>How do I find the rate at a particular time?<\/h3>\n<p>Draw a tangent to the curve at that time and work out its gradient from a large triangle: change in the y quantity divided by change in time.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why do two curves for different concentrations end at the same height?<\/h3>\n<p>If the same limiting amount of reactant is used, the same amount of product forms; the more concentrated run simply gets there sooner.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why put cotton wool in the neck of the flask in the mass-loss method?<\/h3>\n<p>To let the gas escape but stop spray or liquid leaving, so the mass loss is the gas alone.<\/p>\n<\/div>\n<\/div>\n<\/section>\n<section class=\"ols-related-card\">\n<h2>Related Topic 9A Kinetics Pages<\/h2>\n<p>Use these pages to connect the ideas across kinetics and the rest of Topic 9.<\/p>\n<div class=\"ols-related-grid\">\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/collision-theory-and-rates-of-reaction\/\">Collision Theory and Rates of Reaction<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/maxwell-boltzmann-distribution\/\">The Maxwell\u2013Boltzmann Distribution<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/catalysts-and-reaction-profiles\/\">Catalysts and Reaction Profiles<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/\">Topic 9A Kinetics Overview<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-9a-9b-iodine-propanone-and-clock-reaction-kinetics\/\">CP 9A\/9B Iodine\u2013Propanone and Clock Reaction Kinetics<\/a>\n<\/div>\n<\/section>\n<section class=\"ols-attribution-card\">\n        <p><strong>Copyright notice:<\/strong> This OLS revision content, including the explanations, layout, diagrams, tables and embedded learning structure, is authored for Online Learning System by Dr. Mohammed Al-Fatah. It may not be copied, reproduced, redistributed or adapted without written permission.<\/p>\n      <\/section>\n    <\/main>\n  \n\n<script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@graph\": [\n    {\n      \"@type\": \"WebPage\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/measuring-and-calculating-rates\/#webpage\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/9a-kinetics\/measuring-and-calculating-rates\/\",\n      \"name\": \"Measuring and Calculating Rates | Topic 9A Kinetics | Online Learning System\",\n      \"description\": \"Edexcel International A Level Chemistry revision notes on measuring rates: mass, gas volume and clock methods, rate = 1\/time, tangents and initial rate on concentration\u2013time 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