{"id":8082,"date":"2026-09-15T08:24:29","date_gmt":"2026-09-15T07:24:29","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/atom-economy\/"},"modified":"2026-09-19T20:36:29","modified_gmt":"2026-09-19T19:36:29","slug":"atom-economy","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/atom-economy\/","title":{"rendered":"Atom Economy"},"content":{"rendered":"\n<!--\n===============================================================================\nONLINE LEARNING SYSTEM COPYRIGHT NOTICE\n\u00a9 Online Learning System. 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class=\"ols-topic-group\">\n    <h4>Topic 2 Atoms, Molecules and Stoichiometry<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/\">Topic overview<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/atoms-elements-and-molecules\/\">2.1 \/ 2.2 Atoms, Elements and Molecules<\/a><\/li>\n<li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/ions-and-ionic-formulae\/\">2.3 Ions and Ionic Formulae<\/a><\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/equations-and-reaction-types\/\">2.3 Equations and Reaction Types<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/equations-and-reaction-types\/writing-chemical-equations\/\">Writing Chemical Equations<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/equations-and-reaction-types\/typical-reactions-of-acids\/\">Typical Reactions of Acids<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/equations-and-reaction-types\/ionic-and-full-equations\/\">Ionic and Full Equations<\/a><\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/empirical-and-molecular-formulae\/\">2.3 Empirical and Molecular Formulae<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/empirical-and-molecular-formulae\/empirical-formulae\/\">Empirical Formulae<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/empirical-and-molecular-formulae\/molecular-formulae\/\">Molecular Formulae<\/a><\/li>\n<li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/hydrated-salts-and-water-of-crystallisation\/\">2.3 Hydrated Salts and Water of Crystallisation<\/a><\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/\">2.4 Mole Calculations<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/comparing-masses-of-substances\/\">Comparing Masses of Substances<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/calculations-involving-moles\/\">Calculations involving Moles<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/calculations-using-reacting-masses\/\">Calculations using Reacting Masses<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/the-yield-of-a-reaction\/\">The Yield of a Reaction<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/atom-economy\/\">Atom Economy<\/a><\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/calculations-with-solutions-and-gases\/\">2.4 Solutions and Gases<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/calculations-with-solutions-and-gases\/molar-volume-calculations\/\">Molar Volume Calculations<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/calculations-with-solutions-and-gases\/concentrations-of-solutions\/\">Concentrations of Solutions<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/calculations-with-solutions-and-gases\/titration-calculations\/\">Titration Calculations<\/a><\/li>\n        <\/ul>\n      <\/li>\n    <\/ul>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>Other Topics<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-1-atomic-structure\/\">Topic 1 Atomic Structure<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/\">Topic 3 Chemical Bonding<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-4-states-of-matter\/\">Topic 4 States of Matter<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-9-the-periodic-table-chemical-periodicity\/\">Topic 9 Chemical Periodicity<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-13-an-introduction-to-as-level-organic-chemistry\/\">Topic 13 Introduction to Organic Chemistry<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/\">Topic 14 Hydrocarbons<\/a><\/li>\n    <\/ul>\n  <\/div>\n<\/aside>\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\"], 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href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/\">Mole Calculations<\/a> \/\n<span>Atom Economy<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Atom Economy<\/h1>\n        <p class=\"ols-page-intro\">A focused revision guide to percentage atom economy, useful products, waste products and why sustainable chemistry aims to design reactions that make better use of reactant atoms.<\/p>\n\n        <div class=\"ols-badges\">\n<div class=\"ols-badge\">AS Level<\/div>\n<div class=\"ols-badge\">Topic 2: Atoms, Molecules and Stoichiometry<\/div>\n<div class=\"ols-badge\">9701 Papers 1 and 2<\/div>\n<\/div>\n\n        <div class=\"ols-author\">\n          <img decoding=\"async\" class=\"ols-author-avatar-img\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\" alt=\"Dr. Mohammed Al-Fatah\">\n          <div class=\"ols-author-content\">\n            <h2 class=\"ols-author-title\">Written by:<br><span>Dr. Mohammed Al-Fatah<\/span><\/h2>\n            <p class=\"ols-author-description\">Chemistry specialist revision notes for A Level Chemistry.<\/p>\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\"><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\"><\/path><\/svg>\n              View LinkedIn Profile\n            <\/a>\n          <\/div>\n        <\/div>\n      <\/header>\n\n      <section class=\"ols-h5p-card ols-h5p-inline ols-h5p-recap\">\n<span class=\"ols-h5p-kicker\">Before you start<\/span>\n<h2>GCSE Recap: Relative Formula Mass<\/h2>\n<p>Before you start, check that you can work out a relative formula mass when there are brackets and numbers in front.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"313\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">1<\/div><h2>Why Atom Economy Matters<\/h2><\/div>\n        <p>Atom economy measures how efficiently a reaction turns the atoms in the reactants into the <strong>useful product<\/strong>.<\/p>\n        <p>A reaction can have a high percentage yield but still be wasteful if many atoms from the reactants end up in unwanted side products. Atom economy therefore links mole calculations to <strong>sustainable chemistry<\/strong> and industrial process design.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> percentage yield asks how much product was collected. Atom economy asks how many reactant atoms were built into the useful product.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>The Percentage Atom Economy Formula<\/h2><\/div>\n        <p>The percentage atom economy compares the molar mass of useful products with the total molar mass of all reactants in the balanced equation.<\/p>\n        <div class=\"ols-definition-box\"><p><strong>Percentage atom economy = mass of useful products \u00f7 mass of all reactants \u00d7 100<\/strong><\/p><\/div>\n        <p>Use <strong>relative formula masses<\/strong> from the balanced equation. If there is a coefficient in front of a substance, multiply its relative formula mass by that coefficient.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> the numerator includes only the useful product or useful products. The denominator includes all reactants, with balancing numbers taken into account.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Useful Products and Waste Products<\/h2><\/div>\n        <p>The useful product is the substance the reaction is designed to make. Other products may be described as <strong>waste products<\/strong> or <strong>by-products<\/strong>.<\/p>\n        <p>In atom economy questions, first identify which product is useful. Then calculate how much of the total reactant mass becomes that useful product.<\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Term<\/th>\n                <th>Meaning<\/th>\n                <th>Exam implication<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Term\">Useful product<\/td>\n                <td data-label=\"Meaning\">The desired product made by the reaction.<\/td>\n                <td data-label=\"Exam implication\">Include this in the numerator of the atom economy calculation.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Term\">Waste product<\/td>\n                <td data-label=\"Meaning\">An unwanted product formed alongside the useful product.<\/td>\n                <td data-label=\"Exam implication\">Do not include it in the numerator, even though its atoms came from reactants.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Term\">By-product<\/td>\n                <td data-label=\"Meaning\">A secondary product that may be unwanted, but could sometimes be sold or reused.<\/td>\n                <td data-label=\"Exam implication\">Selling a by-product can improve process economics, but it does not change the atom economy calculation.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\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>Quick Check: Set Up an Atom Economy Calculation<\/h2>\n<p>Drag the numbers into place for a reaction this page has not shown you.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-644\" class=\"h5p-iframe\" data-content-id=\"644\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Atom Economy Drag the Words: Setting Up the Calculation\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">4<\/div><h2>Worked Example: Iron from Iron(III) Oxide<\/h2><\/div>\n        <p><strong>Question:<\/strong> Calculate the percentage atom economy for the reaction below if iron is the useful product.<\/p>\n        <p><strong>Balanced equation:<\/strong> Fe<sub>2<\/sub>O<sub>3<\/sub> + 3CO \u2192 2Fe + 3CO<sub>2<\/sub><\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Stage<\/th>\n                <th>Working<\/th>\n                <th>Result<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Stage\">Mass of useful product<\/td>\n                <td data-label=\"Working\">Useful product = Fe<br>2Fe = 2 \u00d7 55.8<\/td>\n                <td data-label=\"Result\">111.6<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Stage\">Mass of all reactants<\/td>\n                <td data-label=\"Working\">Fe<sub>2<\/sub>O<sub>3<\/sub> = 2 \u00d7 55.8 + 3 \u00d7 16 = 159.6<br>3CO = 3 \u00d7 (12 + 16) = 84.0<\/td>\n                <td data-label=\"Result\">243.6<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Stage\">Atom economy<\/td>\n                <td data-label=\"Working\">percentage atom economy = 111.6 \u00f7 243.6 \u00d7 100<\/td>\n                <td data-label=\"Result\">45.8%<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n        <div class=\"ols-key-box\"><p><strong>Answer:<\/strong> the atom economy is <strong>45.8%<\/strong>. This means less than half of the reactant mass becomes the useful iron product.<\/p><\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Calculate Atom Economy<\/h2>\n<p>Work out each atom economy on paper before you flip the card.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-645\" class=\"h5p-iframe\" data-content-id=\"645\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Atom Economy Flip Cards: Calculate It for New Reactions\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">5<\/div><h2>Why One-Product Reactions Have 100% Atom Economy<\/h2><\/div>\n        <p>If a reaction has only one product and all atoms from the reactants are used to make that product, the atom economy is <strong>100%<\/strong>.<\/p>\n        <p>This is why many addition reactions are considered atom-efficient. For example, hydrogen adds across the C=C bond in ethene to make ethane.<\/p>\n        <div class=\"ols-definition-box\"><p><strong>CH<sub>2<\/sub>=CH<sub>2<\/sub> + H<sub>2<\/sub> \u2192 CH<sub>3<\/sub>CH<sub>3<\/sub><\/strong><\/p><\/div>\n        <p>There is only one product, so all atoms from ethene and hydrogen are found in ethane.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Remember:<\/strong> one-product reactions are ideal for atom economy because they do not generate waste products.<\/p><\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Compare Four Routes<\/h2>\n<p>Decide which route to the same product has the lowest atom economy.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-334\" class=\"h5p-iframe\" data-content-id=\"334\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Atom Economy MCQ: Lowest Atom Economy Route to Calcium Chloride\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card orange\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">6<\/div><h2>Atom Economy and Sustainable Chemistry<\/h2><\/div>\n        <p>Sustainable chemistry aims to design processes that reduce waste, reduce separation costs and make better use of starting materials.<\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Feature<\/th>\n                <th>High atom economy<\/th>\n                <th>Low atom economy<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Feature\">Use of atoms<\/td>\n                <td data-label=\"High atom economy\">Most reactant atoms become useful product.<\/td>\n                <td data-label=\"Low atom economy\">Many reactant atoms become waste products.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Feature\">Waste<\/td>\n                <td data-label=\"High atom economy\">Less waste is produced.<\/td>\n                <td data-label=\"Low atom economy\">More waste must be separated, treated or disposed of.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Feature\">Industrial value<\/td>\n                <td data-label=\"High atom economy\">Usually more sustainable and efficient.<\/td>\n                <td data-label=\"Low atom economy\">May be less sustainable unless by-products have useful applications.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\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>Quick Check: Atom Economy, Yield and Waste<\/h2>\n<p>In each round, pick the one statement that is accurate.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-650\" class=\"h5p-iframe\" data-content-id=\"650\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Atom Economy Summary: Yield, Waste and Sustainability\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card orange\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">7<\/div><h2>Common Exam Points<\/h2><\/div>\n        <ul>\n          <li><strong>Atom economy<\/strong> measures the proportion of reactant atoms that become useful product.<\/li>\n          <li>The formula is <strong>mass of useful products \u00f7 mass of all reactants \u00d7 100<\/strong>.<\/li>\n          <li>Use the <strong>balanced equation<\/strong> because coefficients affect the reacting masses.<\/li>\n          <li>The denominator must include <strong>all reactants<\/strong>, not just the limiting reagent.<\/li>\n          <li>The numerator includes only the <strong>useful product<\/strong>, unless more than one product is useful.<\/li>\n          <li>Reactions with only one product have <strong>100% atom economy<\/strong>.<\/li>\n          <li>High atom economy is desirable because it reduces waste and supports sustainable chemistry.<\/li>\n          <li>Selling a by-product may improve the economics of a process, but the atom economy calculation still depends on which product is useful.<\/li>\n        <\/ul>\n      <\/article>\n\n      \n\n      <section class=\"ols-quicksnap-card\">\n        <h2>QuickSnap<\/h2>\n        <p>This text summary condenses the page into the essential exam ideas.<\/p>\n        <ul class=\"ols-quicksnap-list\">\n          <li><strong>Atom economy:<\/strong> the percentage of reactant atoms that end up in the useful product.<\/li>\n          <li><strong>Formula:<\/strong> mass of useful products \u00f7 mass of all reactants \u00d7 100.<\/li>\n          <li><strong>Balanced equation:<\/strong> needed because reacting masses depend on stoichiometric coefficients.<\/li>\n          <li><strong>100% atom economy:<\/strong> usually occurs when there is only one product.<\/li>\n          <li><strong>Low atom economy:<\/strong> means a greater proportion of reactant mass becomes waste or by-products.<\/li>\n          <li><strong>Sustainable chemistry:<\/strong> favours high atom economy because it minimises waste products.<\/li>\n        <\/ul>\n      <\/section>\n\n      <section class=\"ols-faq-card\">\n        <h2>FAQs<\/h2>\n        <p>These questions address common misconceptions students have when learning atom economy calculations.<\/p>\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>What is atom economy?<\/h3>\n            <p>Atom economy is the percentage of reactant atoms that end up in the useful product. It shows how efficiently a reaction uses its starting materials.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>How do you calculate percentage atom economy?<\/h3>\n            <p>Use mass of useful products divided by mass of all reactants, then multiply by 100. The masses are calculated from relative formula masses and the balanced equation.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why do balancing numbers matter in atom economy?<\/h3>\n            <p>Balancing numbers show how many formula units or molecules react. They must be included when calculating the total mass of useful products and the total mass of reactants.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>When is atom economy 100%?<\/h3>\n            <p>Atom economy is 100% when all atoms in the reactants are converted into the useful product. This often occurs in reactions with only one product, such as simple addition reactions.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>What is the difference between percentage yield and atom economy?<\/h3>\n            <p>Percentage yield compares the actual amount obtained with the theoretical amount. Atom economy measures how much of the reactant mass is incorporated into the useful product.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-related-card\">\n        <h2>Related Topics<\/h2>\n        <p>Build the surrounding calculation skills needed for quantitative chemistry.<\/p>\n        <div class=\"ols-related-grid\">\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/the-yield-of-a-reaction\/\">The Yield of a Reaction<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/calculations-using-reacting-masses\/\">Calculations Using Reacting Masses<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/the-yield-of-a-reaction\/\">Percentage Purity<\/a>\n        <\/div>\n      <\/section>\n\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\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\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/atom-economy\/#webpage\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-2-atoms-molecules-and-stoichiometry\/mole-calculations\/atom-economy\/\",\n      \"name\": \"Atom Economy - Cambridge International AS &amp; A Level Chemistry Revision Notes\",\n      \"description\": \"Free Cambridge International AS &amp; A Level Chemistry revision notes on atom economy, useful products, waste products and sustainable chemistry calculations for Topic 2.\",\n      \"inLanguage\": \"en-GB\",\n      \"isPartOf\": {\n     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