{"id":4960,"date":"2026-06-04T05:41:50","date_gmt":"2026-06-04T04:41:50","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/cp-5-hydrolysis-of-halogenoalkanes\/"},"modified":"2026-06-09T10:20:25","modified_gmt":"2026-06-09T09:20:25","slug":"cp-5-hydrolysis-of-halogenoalkanes","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-5-hydrolysis-of-halogenoalkanes\/","title":{"rendered":"CP 5 Hydrolysis of Halogenoalkanes"},"content":{"rendered":"<p><!-- OLS Edexcel International IAL Unit 3 Core Practical page. 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Change<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-3-concentration-of-hcl-by-titration\/\">CP3: Concentration of HCl<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-4-preparation-of-a-standard-solution\/\">CP4: Standard Solution Preparation<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-5-hydrolysis-of-halogenoalkanes\/\">CP5: Halogenoalkane Hydrolysis<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-6-chlorination-of-2-methylpropan-2-ol\/\">CP6: Chlorination of 2-methylpropan-2-ol<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-7-oxidation-of-propan-1-ol\/\">CP7: Oxidation of Propan-1-ol<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-8-analysis-of-inorganic-and-organic-unknowns\/\">CP8: Inorganic & Organic Unknowns<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-9a-9b-iodine-propanone-and-clock-reaction-kinetics\/\">CP9: Iodine-Propanone & Clock Reaction<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-10-activation-energy-of-a-reaction\/\">CP10: Activation Energy<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-11-ka-value-for-a-weak-acid\/\">CP11: Ka Value for Weak Acid<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-12-electrochemical-cells\/\">CP12: Electrochemical Cells<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-13a-13b-redox-titrations\/\">CP13: Redox Titrations<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-14-preparation-of-a-transition-metal-complex\/\">CP14: Transition Metal Complex Prep<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-15-analysis-of-inorganic-and-organic-unknowns\/\">CP15: Inorganic & Organic Unknowns<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-16-preparation-of-aspirin\/\">CP16: Preparation of Aspirin<\/a><\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Useful Links<\/h4>\r\n    <ul class=\"ols-topic-list\">\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Edexcel International Chemistry<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-6-energetics\/\">Energetics<\/a><\/li>\r\n      <li><a href=\"\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/\">Practical Skills<\/a><\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\ndocument.addEventListener('DOMContentLoaded', function () {\r\n  var currentPath = window.location.pathname.replace(\/\\\/$\/, '');\r\n  var sidebarLinks = document.querySelectorAll('.ols-sidebar .ols-topic-list a');\r\n\r\n  sidebarLinks.forEach(function (link) {\r\n    var linkPath = new URL(link.href, window.location.origin).pathname.replace(\/\\\/$\/, '');\r\n\r\n    if (linkPath === currentPath) {\r\n      link.closest('li').classList.add('active');\r\n    } else {\r\n      link.closest('li').classList.remove('active');\r\n    }\r\n  });\r\n});\r\n<\/script><\/div>\n\n  <div class=\"ols-cp-shell\">\n    <main class=\"ols-cp-main\">\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\/core-practicals\/\">Core Practicals<\/a> \/\n        <span>CP5: Rates of Hydrolysis of Halogenoalkanes<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>CP5: Rates of Hydrolysis of Halogenoalkanes<\/h1>\n        <p class=\"ols-page-intro\">In this core practical, you compare how quickly different halogenoalkanes hydrolyse. The rate is measured by timing how long it takes for a silver halide precipitate to appear after aqueous silver nitrate is added.<\/p>\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Exam board: Edexcel International<\/div>\n          <div class=\"ols-badge\">Unit 3: Practical Skills in Chemistry I<\/div>\n          <div class=\"ols-badge\">Core Practical 5<\/div>\n          <div class=\"ols-badge\">Skill: Rates, hydrolysis and nucleophilic substitution<\/div>\n        <\/div>\n        <div class=\"ols-author\">\n          <div class=\"ols-author-avatar\">MA<\/div>\n          <div>\n            <p><strong>Written by: Dr. Mohammed Al-Fatah<\/strong><\/p>\n            <p>Chemistry specialist revision notes for Edexcel International A Level Chemistry.<\/p>\n          <\/div>\n        <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">1<\/div>\n          <h2>What This Practical Is Testing<\/h2>\n        <\/div>\n        <p>This practical compares the <strong>relative rates of hydrolysis<\/strong> of different halogenoalkanes. Hydrolysis is the reaction of a molecule with water. For halogenoalkanes, water acts as a nucleophile and the product is an alcohol plus a halide ion.<\/p>\n        <p>The experiment has two linked comparisons. In <strong>Part 1<\/strong>, you compare primary chloro-, bromo- and iodoalkanes. In <strong>Part 2<\/strong>, you compare primary, secondary and tertiary bromoalkanes.<\/p>\n\n        <div class=\"ols-process-grid\" aria-label=\"CP5 practical process map\">\n          <div class=\"ols-process-step\">\n            <span>1<\/span>\n            <h3>Hydrolyse<\/h3>\n            <p>Water reacts with the halogenoalkane and releases a halide ion, X<sup>&#8211;<\/sup>.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>2<\/span>\n            <h3>Detect<\/h3>\n            <p>Ag<sup>+<\/sup> ions from silver nitrate react with X<sup>&#8211;<\/sup> to form a silver halide precipitate.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>3<\/span>\n            <h3>Compare<\/h3>\n            <p>The shorter the time taken for cloudiness to appear, the faster the hydrolysis reaction.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Key idea:<\/strong> Silver nitrate does not cause the hydrolysis. It provides Ag<sup>+<\/sup> ions so the halide ion formed by hydrolysis can be detected as a precipitate.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">2<\/div>\n          <h2>Safety and Apparatus<\/h2>\n        <\/div>\n        <p>Wear eye protection and avoid skin contact with the reactants. Ethanol and halogenoalkanes are highly flammable, so there must be <strong>no naked flames<\/strong>. The laboratory should also be well ventilated because halogenoalkanes can produce fumes.<\/p>\n\n        <div class=\"ols-apparatus-grid\">\n          <div class=\"ols-apparatus-card\">\n            <h3>Solutions and chemicals<\/h3>\n            <p>1-chlorobutane, 1-bromobutane, 1-iodobutane, 2-bromobutane, 2-bromo-2-methylpropane, ethanol and 0.05 mol dm<sup>-3<\/sup> silver nitrate solution.<\/p>\n          <\/div>\n          <div class=\"ols-apparatus-card\">\n            <h3>Equipment<\/h3>\n            <p>250 cm<sup>3<\/sup> beaker, test tubes with bungs, dropping pipettes, measuring cylinders, labels, stop clock and a kettle for preparing the warm water bath.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card green\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">3<\/div>\n          <h2>The Five Halogenoalkanes Used<\/h2>\n        <\/div>\n        <p>Before interpreting the results, identify which halogenoalkanes are primary, secondary and tertiary. This matters because Part 2 compares how the structure of the halogenoalkane affects the rate of hydrolysis.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Halogenoalkane<\/th>\n                <th>Classification<\/th>\n                <th>Where it is used<\/th>\n                <th>Comparison being made<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td><strong>1-chlorobutane<\/strong><\/td>\n                <td>Primary<\/td>\n                <td>Part 1<\/td>\n                <td>Effect of different halogens<\/td>\n              <\/tr>\n              <tr>\n                <td><strong>1-bromobutane<\/strong><\/td>\n                <td>Primary<\/td>\n                <td>Part 1 and Part 2<\/td>\n                <td>Halogen comparison and structure comparison<\/td>\n              <\/tr>\n              <tr>\n                <td><strong>1-iodobutane<\/strong><\/td>\n                <td>Primary<\/td>\n                <td>Part 1<\/td>\n                <td>Effect of different halogens<\/td>\n              <\/tr>\n              <tr>\n                <td><strong>2-bromobutane<\/strong><\/td>\n                <td>Secondary<\/td>\n                <td>Part 2<\/td>\n                <td>Effect of primary, secondary and tertiary structure<\/td>\n              <\/tr>\n              <tr>\n                <td><strong>2-bromo-2-methylpropane<\/strong><\/td>\n                <td>Tertiary<\/td>\n                <td>Part 2<\/td>\n                <td>Effect of primary, secondary and tertiary structure<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image contain structure-classification-small\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/06\/Chemical-structure-classification-table.webp\" alt=\"Chemical structure classification table showing primary, secondary and tertiary halogenoalkanes used in CP5.\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <h3>Primary, secondary and tertiary halogenoalkanes<\/h3>\n            <p>Use the carbon bonded to the halogen to classify the halogenoalkane. Primary, secondary and tertiary structures are compared in Part 2 of the practical.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">4<\/div>\n          <h2>Method: How the Rate Is Measured<\/h2>\n        <\/div>\n        <p>The reaction is carried out in a warm water bath at about <strong>50 \u00b0C<\/strong>. This keeps the temperature controlled, because temperature affects the rate of reaction.<\/p>\n\n        <div class=\"ols-process-grid\" aria-label=\"CP5 method sequence\">\n          <div class=\"ols-process-step\">\n            <span>1<\/span>\n            <h3>Prepare water bath<\/h3>\n            <p>Fill a 250 cm<sup>3<\/sup> beaker about three-quarters full with water at around 50 \u00b0C.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>2<\/span>\n            <h3>Add ethanol<\/h3>\n            <p>Add 5 cm<sup>3<\/sup> ethanol to each labelled test tube.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>3<\/span>\n            <h3>Add halogenoalkane<\/h3>\n            <p>Add four drops of the relevant halogenoalkane to each ethanol tube.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>4<\/span>\n            <h3>Warm both solutions<\/h3>\n            <p>Warm the halogenoalkane mixtures and silver nitrate test tubes in the same water bath.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>5<\/span>\n            <h3>Mix and time<\/h3>\n            <p>Add silver nitrate to the halogenoalkane mixture and start the stop clock at the same time.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>6<\/span>\n            <h3>Stop when cloudy<\/h3>\n            <p>Stop timing as soon as the solution becomes cloudy due to a silver halide precipitate.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Technique point:<\/strong> The test tubes containing the reacting mixture should stay in the water bath while timing. Otherwise, the temperature may fall and the rate comparison becomes less reliable.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">5<\/div>\n          <h2>What Happens During Hydrolysis?<\/h2>\n        <\/div>\n        <p>Hydrolysis of a halogenoalkane is a <strong>nucleophilic substitution reaction<\/strong>. Water acts as the nucleophile because the oxygen atom has lone pairs of electrons. It attacks the electron-deficient carbon atom attached to the halogen.<\/p>\n        <p>The C-X bond breaks and the halide ion leaves. The products are an alcohol, a hydrogen ion and a halide ion.<\/p>\n        <span class=\"ols-equation\">R-X + H<sub>2<\/sub>O \u2192 R-OH + H<sup>+<\/sup> + X<sup>&#8211;<\/sup><\/span>\n        <span class=\"ols-equation\">CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>Br + H<sub>2<\/sub>O \u2192 CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>OH + H<sup>+<\/sup> + Br<sup>&#8211;<\/sup><\/span>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/06\/Mechanism-of-nucleophilic-attack-reaction.webp\" alt=\"Mechanism of nucleophilic attack reaction showing water attacking the carbon bonded to a halogen in a halogenoalkane.\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <h3>Nucleophilic substitution by water<\/h3>\n            <p>The lone pair on oxygen attacks the \u03b4+ carbon. The C-X bond breaks, forming an alcohol, H<sup>+<\/sup> and X<sup>&#8211;<\/sup>.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card gold\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">6<\/div>\n          <h2>Why Ethanol, Water and Silver Nitrate Are Used<\/h2>\n        <\/div>\n        <p>Each chemical has a specific role. This is a common exam area because students often mix up the solvent, nucleophile and test reagent.<\/p>\n\n        <div class=\"ols-apparatus-grid\">\n          <div class=\"ols-apparatus-card\">\n            <h3>Ethanol<\/h3>\n            <p>Halogenoalkanes are insoluble in water. Ethanol helps the halogenoalkane dissolve so it can react with water molecules.<\/p>\n          <\/div>\n          <div class=\"ols-apparatus-card\">\n            <h3>Water<\/h3>\n            <p>Water is the nucleophile in this practical. It reacts with the halogenoalkane during hydrolysis.<\/p>\n          <\/div>\n          <div class=\"ols-apparatus-card\">\n            <h3>Silver nitrate<\/h3>\n            <p>Ag<sup>+<\/sup> ions react with the halide ion released during hydrolysis, forming a silver halide precipitate.<\/p>\n          <\/div>\n          <div class=\"ols-apparatus-card\">\n            <h3>Why not hydroxide?<\/h3>\n            <p>If hydroxide ions are present when AgNO<sub>3<\/sub> is added, a precipitate of silver oxide or silver hydroxide can interfere with the test.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Exam wording:<\/strong> Do not write \u201cethanol is the nucleophile\u201d. In this practical, ethanol is used to help dissolve the halogenoalkane. Water is the nucleophile.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card cyan\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">7<\/div>\n          <h2>How the Silver Halide Precipitate Shows the Rate<\/h2>\n        <\/div>\n        <p>The precipitate only appears after hydrolysis has produced halide ions. Therefore, the time taken for cloudiness to appear tells you how quickly the halogenoalkane has hydrolysed.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Halide ion formed<\/th>\n                <th>Silver halide precipitate<\/th>\n                <th>Colour<\/th>\n                <th>What it shows<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td>Cl<sup>&#8211;<\/sup><\/td>\n                <td>AgCl<\/td>\n                <td>White<\/td>\n                <td>A chloroalkane has hydrolysed.<\/td>\n              <\/tr>\n              <tr>\n                <td>Br<sup>&#8211;<\/sup><\/td>\n                <td>AgBr<\/td>\n                <td>Cream<\/td>\n                <td>A bromoalkane has hydrolysed.<\/td>\n              <\/tr>\n              <tr>\n                <td>I<sup>&#8211;<\/sup><\/td>\n                <td>AgI<\/td>\n                <td>Yellow<\/td>\n                <td>An iodoalkane has hydrolysed.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/06\/Precipitate-colours-in-halogenoalkanes-test.webp\" alt=\"Precipitate colours in the hydrolysis of halogenoalkanes showing cream, white and yellow silver halide precipitates.\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <h3>Precipitate colours in the halogenoalkane test<\/h3>\n            <p>Silver chloride is white, silver bromide is cream and silver iodide is yellow. The colour identifies the halide ion released during hydrolysis.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">8<\/div>\n          <h2>Part 1: Comparing Chloro-, Bromo- and Iodoalkanes<\/h2>\n        <\/div>\n        <p>In Part 1, the halogenoalkanes are all primary. This means the main variable is the halogen: chlorine, bromine or iodine.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Halogenoalkane<\/th>\n                <th>C-X bond<\/th>\n                <th>Time for precipitate to form \/ s<\/th>\n                <th>Rate conclusion<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr class=\"ols-highlight-fast\">\n                <td>1-iodobutane<\/td>\n                <td>C-I<\/td>\n                <td>52<\/td>\n                <td>Fastest<\/td>\n              <\/tr>\n              <tr>\n                <td>1-bromobutane<\/td>\n                <td>C-Br<\/td>\n                <td>87<\/td>\n                <td>Intermediate<\/td>\n              <\/tr>\n              <tr class=\"ols-highlight-slow\">\n                <td>1-chlorobutane<\/td>\n                <td>C-Cl<\/td>\n                <td>606<\/td>\n                <td>Slowest<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-rate-strip\">\n          <div class=\"ols-rate-pill\">\n            <small>C-I bond<\/small>\n            <strong>218 kJ mol<sup>-1<\/sup><\/strong>\n            <span>Weakest bond, so it breaks most easily.<\/span>\n          <\/div>\n          <div class=\"ols-rate-pill\">\n            <small>C-Br bond<\/small>\n            <strong>284 kJ mol<sup>-1<\/sup><\/strong>\n            <span>Intermediate bond strength and intermediate rate.<\/span>\n          <\/div>\n          <div class=\"ols-rate-pill\">\n            <small>C-Cl bond<\/small>\n            <strong>339 kJ mol<sup>-1<\/sup><\/strong>\n            <span>Strongest bond, so it breaks most slowly.<\/span>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Conclusion:<\/strong> The rate order is iodoalkane &gt; bromoalkane &gt; chloroalkane because the C-I bond is weakest and the C-Cl bond is strongest.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card green\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">9<\/div>\n          <h2>Part 2: Comparing Primary, Secondary and Tertiary Bromoalkanes<\/h2>\n        <\/div>\n        <p>In Part 2, the halogen is kept the same because all three compounds are bromoalkanes. This means the main variable is whether the halogenoalkane is primary, secondary or tertiary.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Halogenoalkane<\/th>\n                <th>Classification<\/th>\n                <th>Time for precipitate to form \/ s<\/th>\n                <th>Rate conclusion<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr class=\"ols-highlight-fast\">\n                <td>2-bromo-2-methylpropane<\/td>\n                <td>Tertiary<\/td>\n                <td>3<\/td>\n                <td>Fastest<\/td>\n              <\/tr>\n              <tr>\n                <td>2-bromobutane<\/td>\n                <td>Secondary<\/td>\n                <td>34<\/td>\n                <td>Intermediate<\/td>\n              <\/tr>\n              <tr class=\"ols-highlight-slow\">\n                <td>1-bromobutane<\/td>\n                <td>Primary<\/td>\n                <td>59<\/td>\n                <td>Slowest<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Conclusion:<\/strong> For these bromoalkanes, the observed rate order is tertiary &gt; secondary &gt; primary. A shorter time means a faster hydrolysis reaction.<\/p>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/06\/Comparing-halogenoalkane-hydrolysis-rates.webp\" alt=\"Infographic comparing the rates of hydrolysis of halogenoalkanes using silver nitrate precipitate formation.\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <h3>Comparing rates using precipitate formation<\/h3>\n            <p>The faster the precipitate forms, the faster the halogenoalkane has hydrolysed. The timing data are used to rank the relative rates.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <section class=\"ols-interactive-card\" aria-label=\"Interactive CP5 data walkthrough\">\n        <div class=\"ols-interactive-head\">\n          <div>\n            <h2>Interactive: From Cloudiness to Rate Order<\/h2>\n            <p>Reveal the data in stages. The aim is to connect the time taken for the precipitate to appear with the rate of hydrolysis and the chemistry behind the trend.<\/p>\n          <\/div>\n          <button type=\"button\" class=\"ols-reset-btn\" id=\"olsCp5Reset\">Reset<\/button>\n        <\/div>\n\n        <div class=\"ols-interactive-grid\">\n          <div class=\"ols-interactive-panel\">\n            <h3>Results board<\/h3>\n            <p><strong>Part 1:<\/strong> Comparing primary chloro-, bromo- and iodoalkanes.<\/p>\n            <table class=\"ols-mini-results\" aria-label=\"Interactive Part 1 halogenoalkane data\">\n              <thead>\n                <tr>\n                  <th>Halogenoalkane<\/th>\n                  <th>Bond<\/th>\n                  <th>Time \/ s<\/th>\n                  <th>Rate<\/th>\n                <\/tr>\n              <\/thead>\n              <tbody>\n                <tr id=\"olsCp5P1I\"><td>1-iodobutane<\/td><td>C-I<\/td><td><span class=\"ols-hidden-value\" data-value=\"52\">?<\/span><\/td><td><span class=\"ols-hidden-value\" data-value=\"Fastest\">?<\/span><\/td><\/tr>\n                <tr id=\"olsCp5P1Br\"><td>1-bromobutane<\/td><td>C-Br<\/td><td><span class=\"ols-hidden-value\" data-value=\"87\">?<\/span><\/td><td><span class=\"ols-hidden-value\" data-value=\"Intermediate\">?<\/span><\/td><\/tr>\n                <tr id=\"olsCp5P1Cl\"><td>1-chlorobutane<\/td><td>C-Cl<\/td><td><span class=\"ols-hidden-value\" data-value=\"606\">?<\/span><\/td><td><span class=\"ols-hidden-value\" data-value=\"Slowest\">?<\/span><\/td><\/tr>\n              <\/tbody>\n            <\/table>\n\n            <p style=\"margin-top:18px;\"><strong>Part 2:<\/strong> Comparing primary, secondary and tertiary bromoalkanes.<\/p>\n            <table class=\"ols-mini-results\" aria-label=\"Interactive Part 2 halogenoalkane data\">\n              <thead>\n                <tr>\n                  <th>Halogenoalkane<\/th>\n                  <th>Type<\/th>\n                  <th>Time \/ s<\/th>\n                  <th>Rate<\/th>\n                <\/tr>\n              <\/thead>\n              <tbody>\n                <tr id=\"olsCp5P2T\"><td>2-bromo-2-methylpropane<\/td><td>Tertiary<\/td><td><span class=\"ols-hidden-value\" data-value=\"3\">?<\/span><\/td><td><span class=\"ols-hidden-value\" data-value=\"Fastest\">?<\/span><\/td><\/tr>\n                <tr id=\"olsCp5P2S\"><td>2-bromobutane<\/td><td>Secondary<\/td><td><span class=\"ols-hidden-value\" data-value=\"34\">?<\/span><\/td><td><span class=\"ols-hidden-value\" data-value=\"Intermediate\">?<\/span><\/td><\/tr>\n                <tr id=\"olsCp5P2P\"><td>1-bromobutane<\/td><td>Primary<\/td><td><span class=\"ols-hidden-value\" data-value=\"59\">?<\/span><\/td><td><span class=\"ols-hidden-value\" data-value=\"Slowest\">?<\/span><\/td><\/tr>\n              <\/tbody>\n            <\/table>\n          <\/div>\n\n          <div class=\"ols-interactive-panel\">\n            <h3>Walkthrough controls<\/h3>\n            <div class=\"ols-action-stack\">\n              <button type=\"button\" class=\"ols-action-btn is-pulse\" data-step=\"1\">1. Reveal Part 1 times<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"2\">2. Rank C-I, C-Br and C-Cl<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"3\">3. Connect rate to bond strength<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"4\">4. Reveal Part 2 times<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"5\">5. Rank primary, secondary and tertiary<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"6\">6. Build the exam conclusion<\/button>\n            <\/div>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-interactive-panel\" style=\"margin-top:18px;\">\n          <div class=\"ols-working-box\" id=\"olsCp5Working\">\n            <h4>Start here<\/h4>\n            <p>Click the first button to reveal the Part 1 timing data. Remember: the precipitate forms only after hydrolysis has released a halide ion.<\/p>\n            <p class=\"ols-equation\">shorter time = faster hydrolysis<\/p>\n          <\/div>\n        <\/div>\n\n        <script>\n          (function(){\n            var root = document.currentScript.closest('.ols-interactive-card');\n            if (!root) return;\n            var buttons = root.querySelectorAll('.ols-action-btn');\n            var reset = root.querySelector('#olsCp5Reset');\n            var working = root.querySelector('#olsCp5Working');\n            var rows = ['olsCp5P1I','olsCp5P1Br','olsCp5P1Cl','olsCp5P2T','olsCp5P2S','olsCp5P2P'];\n\n            function revealRows(ids){\n              ids.forEach(function(id){\n                var row = root.querySelector('#' + id);\n                if (!row) return;\n                row.querySelectorAll('.ols-hidden-value').forEach(function(el){\n                  el.textContent = el.getAttribute('data-value');\n                  el.classList.remove('ols-hidden-value');\n                  el.classList.add('ols-visible-value');\n                });\n              });\n            }\n\n            function clearHighlights(){\n              rows.forEach(function(id){\n                var row = root.querySelector('#' + id);\n                if (row) row.classList.remove('ols-row-fast','ols-row-slow');\n              });\n            }\n\n            function setActive(step){\n              buttons.forEach(function(btn){\n                btn.classList.toggle('is-active', btn.getAttribute('data-step') === String(step));\n                btn.classList.remove('is-pulse');\n              });\n              var next = root.querySelector('.ols-action-btn[data-step=\"' + (Number(step) + 1) + '\"]');\n              if (next) next.classList.add('is-pulse');\n            }\n\n            function resetAll(){\n              rows.forEach(function(id){\n                var row = root.querySelector('#' + id);\n                if (!row) return;\n                row.classList.remove('ols-row-fast','ols-row-slow');\n                row.querySelectorAll('.ols-visible-value').forEach(function(el){\n                  el.textContent = '?';\n                  el.classList.remove('ols-visible-value');\n                  el.classList.add('ols-hidden-value');\n                });\n              });\n              buttons.forEach(function(btn){ btn.classList.remove('is-active','is-pulse'); });\n              var first = root.querySelector('.ols-action-btn[data-step=\"1\"]');\n              if (first) first.classList.add('is-pulse');\n              working.innerHTML = '<h4>Start here<\/h4><p>Click the first button to reveal the Part 1 timing data. Remember: the precipitate forms only after hydrolysis has released a halide ion.<\/p><p class=\"ols-equation\">shorter time = faster hydrolysis<\/p>';\n            }\n\n            buttons.forEach(function(btn){\n              btn.addEventListener('click', function(){\n                var step = Number(btn.getAttribute('data-step'));\n                clearHighlights();\n                setActive(step);\n\n                if (step === 1) {\n                  revealRows(['olsCp5P1I','olsCp5P1Br','olsCp5P1Cl']);\n                  working.innerHTML = '<h4>Step 1: Part 1 times<\/h4><p>The primary halogenoalkanes give times of 52 s, 87 s and 606 s.<\/p><p>The precipitate appears first for 1-iodobutane and last for 1-chlorobutane.<\/p>';\n                }\n\n                if (step === 2) {\n                  revealRows(['olsCp5P1I','olsCp5P1Br','olsCp5P1Cl']);\n                  root.querySelector('#olsCp5P1I').classList.add('ols-row-fast');\n                  root.querySelector('#olsCp5P1Cl').classList.add('ols-row-slow');\n                  working.innerHTML = '<h4>Step 2: Rank the rates<\/h4><p>A shorter time means faster hydrolysis.<\/p><p class=\"ols-answer-pill\">Rate order: iodoalkane &gt; bromoalkane &gt; chloroalkane<\/p>';\n                }\n\n                if (step === 3) {\n                  revealRows(['olsCp5P1I','olsCp5P1Br','olsCp5P1Cl']);\n                  root.querySelector('#olsCp5P1I').classList.add('ols-row-fast');\n                  root.querySelector('#olsCp5P1Cl').classList.add('ols-row-slow');\n                  working.innerHTML = '<h4>Step 3: Connect to bond strength<\/h4><p>C-I = 218 kJ mol<sup>-1<\/sup>, C-Br = 284 kJ mol<sup>-1<\/sup>, C-Cl = 339 kJ mol<sup>-1<\/sup>.<\/p><p>The C-I bond is weakest, so it breaks most easily. The C-Cl bond is strongest, so it breaks most slowly.<\/p>';\n                }\n\n                if (step === 4) {\n                  revealRows(['olsCp5P2T','olsCp5P2S','olsCp5P2P']);\n                  working.innerHTML = '<h4>Step 4: Part 2 times<\/h4><p>The bromoalkanes give times of 3 s, 34 s and 59 s.<\/p><p>The tertiary bromoalkane gives a precipitate first.<\/p>';\n                }\n\n                if (step === 5) {\n                  revealRows(['olsCp5P2T','olsCp5P2S','olsCp5P2P']);\n                  root.querySelector('#olsCp5P2T').classList.add('ols-row-fast');\n                  root.querySelector('#olsCp5P2P').classList.add('ols-row-slow');\n                  working.innerHTML = '<h4>Step 5: Rank structure<\/h4><p>For these bromoalkanes, the observed rate order is:<\/p><p class=\"ols-answer-pill\">tertiary &gt; secondary &gt; primary<\/p>';\n                }\n\n                if (step === 6) {\n                  revealRows(['olsCp5P1I','olsCp5P1Br','olsCp5P1Cl','olsCp5P2T','olsCp5P2S','olsCp5P2P']);\n                  root.querySelector('#olsCp5P1I').classList.add('ols-row-fast');\n                  root.querySelector('#olsCp5P1Cl').classList.add('ols-row-slow');\n                  root.querySelector('#olsCp5P2T').classList.add('ols-row-fast');\n                  root.querySelector('#olsCp5P2P').classList.add('ols-row-slow');\n                  working.innerHTML = '<h4>Step 6: Exam conclusion<\/h4><p>The rate is judged by the time taken for the precipitate to appear. A shorter time means faster hydrolysis.<\/p><p>In Part 1, iodoalkanes hydrolyse fastest because the C-I bond is weakest. In Part 2, the tertiary bromoalkane reacts fastest, followed by the secondary and then the primary bromoalkane.<\/p>';\n                }\n              });\n            });\n\n            if (reset) reset.addEventListener('click', resetAll);\n          })();\n        <\/script>\n      <\/section>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">10<\/div>\n          <h2>Exam-Style Data Interpretation<\/h2>\n        <\/div>\n        <p>A common exam version compares equal amounts of 2-chloropropane, 2-bromopropane and 2-iodopropane. The same logic applies: shorter time means faster hydrolysis.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Halogenoalkane<\/th>\n                <th>Time for precipitate to form \/ s<\/th>\n                <th>Halogen electronegativity<\/th>\n                <th>Mean C-halogen bond strength \/ kJ mol<sup>-1<\/sup><\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr class=\"ols-highlight-fast\">\n                <td>2-iodopropane<\/td>\n                <td>31<\/td>\n                <td>2.7<\/td>\n                <td>218<\/td>\n              <\/tr>\n              <tr>\n                <td>2-bromopropane<\/td>\n                <td>74<\/td>\n                <td>3.0<\/td>\n                <td>284<\/td>\n              <\/tr>\n              <tr class=\"ols-highlight-slow\">\n                <td>2-chloropropane<\/td>\n                <td>241<\/td>\n                <td>3.2<\/td>\n                <td>339<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-qa-grid\">\n          <div class=\"ols-qa-card\">\n            <h3>Why use equal moles?<\/h3>\n            <p>Equal moles means the concentration of halogenoalkane is equal in each experiment, so concentration does not affect the relative rates.<\/p>\n          <\/div>\n          <div class=\"ols-qa-card\">\n            <h3>Why is electronegativity not the controlling factor?<\/h3>\n            <p>Chlorine is most electronegative, so it would make the carbon most \u03b4+. If electronegativity controlled the rate, chloroalkanes would react fastest. The data show the opposite.<\/p>\n          <\/div>\n          <div class=\"ols-qa-card\">\n            <h3>Why does bond strength explain the trend?<\/h3>\n            <p>The carbon-halogen bond breaks during the reaction. A stronger bond is harder to break and gives a higher activation energy, so the reaction is slower.<\/p>\n          <\/div>\n          <div class=\"ols-qa-card\">\n            <h3>Final exam conclusion<\/h3>\n            <p>The C-I bond is weakest, so iodoalkanes hydrolyse fastest. The C-Cl bond is strongest, so chloroalkanes hydrolyse slowest.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">11<\/div>\n          <h2>Core Practical Questions and Answers<\/h2>\n        <\/div>\n        <p>Use these as compact revision checks. They cover the main questions students are expected to answer from the practical.<\/p>\n\n        <div class=\"ols-qa-grid\">\n          <div class=\"ols-qa-card\">\n            <h3>Write the equation for 1-bromobutane with water.<\/h3>\n            <p>CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>Br + H<sub>2<\/sub>O \u2192 CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>OH + H<sup>+<\/sup> + Br<sup>&#8211;<\/sup><\/p>\n          <\/div>\n          <div class=\"ols-qa-card\">\n            <h3>What precipitate forms from 1-iodobutane?<\/h3>\n            <p>Silver iodide, AgI. It is a yellow precipitate.<\/p>\n          <\/div>\n          <div class=\"ols-qa-card\">\n            <h3>Why is ethanol used?<\/h3>\n            <p>Halogenoalkanes are insoluble in water. Ethanol helps them dissolve so they can react with water molecules.<\/p>\n          <\/div>\n          <div class=\"ols-qa-card\">\n            <h3>Why can water act as a nucleophile?<\/h3>\n            <p>The oxygen atom in water has lone pairs of electrons that can attack the electron-deficient carbon atom.<\/p>\n          <\/div>\n          <div class=\"ols-qa-card\">\n            <h3>Why is water used rather than hydroxide ions?<\/h3>\n            <p>Hydroxide ions would form a precipitate with silver ions immediately, interfering with the silver nitrate test.<\/p>\n          <\/div>\n          <div class=\"ols-qa-card\">\n            <h3>Classify the five halogenoalkanes used.<\/h3>\n            <p>1-chlorobutane, 1-bromobutane and 1-iodobutane are primary. 2-bromobutane is secondary. 2-bromo-2-methylpropane is tertiary.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card gold\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">12<\/div>\n          <h2>Common Mistakes<\/h2>\n        <\/div>\n\n        <div class=\"ols-error-grid\">\n          <div class=\"ols-error-card\">\n            <h3>Mistake: \u201cSilver nitrate causes hydrolysis.\u201d<\/h3>\n            <p><strong>Fix:<\/strong> Water hydrolyses the halogenoalkane. Silver nitrate detects the halide ion produced.<\/p>\n          <\/div>\n          <div class=\"ols-error-card\">\n            <h3>Mistake: \u201cYellow precipitate means iodine was present.\u201d<\/h3>\n            <p><strong>Fix:<\/strong> Yellow AgI means iodide ions formed after hydrolysis, so the original compound was an iodoalkane.<\/p>\n          <\/div>\n          <div class=\"ols-error-card\">\n            <h3>Mistake: \u201cElectronegativity controls the rate.\u201d<\/h3>\n            <p><strong>Fix:<\/strong> The data show bond strength is the better explanation here. C-I is weakest and reacts fastest.<\/p>\n          <\/div>\n          <div class=\"ols-error-card\">\n            <h3>Mistake: Forgetting ethanol\u2019s role.<\/h3>\n            <p><strong>Fix:<\/strong> Ethanol helps dissolve the halogenoalkane. It is not the nucleophile in the hydrolysis explanation.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n      <section class=\"ols-faq-card\">\n        <h2>CP5 FAQs<\/h2>\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>How is the rate measured in CP5?<\/h3>\n            <p>The rate is compared by measuring the time taken for a silver halide precipitate to appear. A shorter time means faster hydrolysis.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why does 1-iodobutane react faster than 1-chlorobutane?<\/h3>\n            <p>The C-I bond is weaker than the C-Cl bond, so it breaks more easily. This makes iodoalkanes hydrolyse faster than chloroalkanes.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why is ethanol used in the practical?<\/h3>\n            <p>Halogenoalkanes do not dissolve well in water. Ethanol helps dissolve the halogenoalkane so it can react with water.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why must there be no naked flames?<\/h3>\n            <p>Ethanol and halogenoalkanes are highly flammable, so naked flames would create a fire risk.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>What is the role of silver nitrate?<\/h3>\n            <p>Silver nitrate provides Ag<sup>+<\/sup> ions. These react with released halide ions to form silver halide precipitates.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n    <\/main>\n  <\/div>\n<\/section>\n","protected":false},"excerpt":{"rendered":"<p>Revision Notes \/ A Level Chemistry \/ Edexcel International \/ Core Practicals \/ CP5: Rates of Hydrolysis of Halogenoalkanes CP5: Rates of Hydrolysis of Halogenoalkanes In this core practical, you compare how quickly different halogenoalkanes hydrolyse. The rate is measured by timing how long it takes for a silver halide precipitate to appear after aqueous [&hellip;]<\/p>\n","protected":false},"author":12,"featured_media":0,"parent":5028,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-4960","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4960","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/comments?post=4960"}],"version-history":[{"count":0,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4960\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/5028"}],"wp:attachment":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media?parent=4960"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}