{"id":5280,"date":"2026-06-19T04:55:14","date_gmt":"2026-06-19T03:55:14","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/ionic-equations\/"},"modified":"2026-09-19T20:35:45","modified_gmt":"2026-09-19T19:35:45","slug":"ionic-equations","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/ionic-equations\/","title":{"rendered":"Ionic Equations"},"content":{"rendered":"\n<!--\n===============================================================================\nONLINE LEARNING SYSTEM COPYRIGHT NOTICE\n\u00a9 Online Learning System. 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href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/relative-masses\/\">Relative Masses<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/the-mole-and-avogadro-constant\/\">The Mole and Avogadro Constant<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/empirical-and-molecular-formulae\/\">Empirical and Molecular Formulae<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/empirical-and-molecular-formulae\/empirical-formula\/\">Empirical Formula<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/empirical-and-molecular-formulae\/molecular-formula\/\">Molecular Formula<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/\">Chemical Equations and Reacting Masses<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/writing-chemical-equations\/\">Writing Chemical Equations<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/ionic-equations\/\">Ionic Equations<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/calculations-using-reacting-masses\/\">Calculations Using Reacting Masses<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/concentration-and-titration-calculations\/\">Concentration and Titration Calculations<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/concentration-and-titration-calculations\/concentrations-of-solutions\/\">Concentrations of Solutions<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/concentration-and-titration-calculations\/titration-calculations\/\">Titration Calculations<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/gas-volumes-and-the-ideal-gas-equation\/\">Gas Volumes and the Ideal Gas Equation<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/percentage-yield\/\">Percentage Yield<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/atom-economy\/\">Atom Economy<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Adjacent Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-1-atomicstructure\/\">3.1.1 Atomic Structure<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/\">3.1.3 Bonding<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-4-energetics\/\">3.1.4 Energetics<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-2-1-periodicity\/\">3.2.1 Periodicity<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\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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true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', highlightActive);\r\n  }\r\n})();\r\n<\/script>\n\n<main class=\"ols-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\/aqa\/\">AQA<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/\">3.1.2 Amount of Substance<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/\">Chemical Equations and Reacting Masses<\/a> \/\n        <span>Ionic Equations<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Ionic Equations<\/h1>\n        <p class=\"ols-page-intro\">AQA revision notes on ionic equations, spectator ions, state symbols and precipitation reactions. Ionic equations show the reacting particles after unchanged spectator ions have been removed.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Paper 1 and Paper 2<\/div>\n          <div class=\"ols-badge\">AQA<\/div>\n          <div class=\"ols-badge\">3.1.2 Amount of Substance<\/div>\n          <div class=\"ols-badge\">7405\/1 and 7405\/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: Ions, Formulae and State Symbols<\/h2>\n<p>Before you start, check that you can build a formula from its ions and use state symbols.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"288\"><\/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 Ionic Equations Are Useful<\/h2><\/div>\n        <p>An <strong>ionic equation<\/strong> shows the ions and particles that actually take part in a reaction. It leaves out ions that remain unchanged in solution.<\/p>\n        <p>This is why ionic equations are often shorter than full chemical equations. They remove spectator ions and focus on the reacting species.<\/p>\n        <div class=\"ols-definition-box\"><p><strong>Ionic equation:<\/strong> an equation that represents a reaction using the reacting ions or particles, with spectator ions removed.<\/p><\/div>\n        <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> full equations show every formula in the reaction mixture, while ionic equations show the actual chemical change.<\/p><\/div>\n      <\/article>\n\n      <div class=\"ols-zoom-card\">\n        <div class=\"ols-zoom-card-image\">\n          <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Understanding-ionic-equations-in-chemistry.webp\" alt=\"Understanding ionic equations in chemistry with reacting ions and spectator ions\" class=\"ols-zoomable-img ols-lightbox-target\" draggable=\"false\">\n        <\/div>\n        <div class=\"ols-zoom-card-caption\">\n          <p>Ionic equations focus attention on the particles that react, rather than every ion present in the solution.<\/p>\n        <\/div>\n      <\/div>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>Ions in Aqueous Solution<\/h2><\/div>\n        <p>When a soluble ionic compound dissolves in water, its ions separate and move around in solution. For example, sodium chloride solution contains <strong>Na<sup>+<\/sup>(aq)<\/strong> ions and <strong>Cl<sup>&#8211;<\/sup>(aq)<\/strong> ions.<\/p>\n        <p>The state symbol <strong>(aq)<\/strong> means <strong>aqueous<\/strong>, which means dissolved in water. It is important because ionic equations often involve dissolved ions.<\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>State symbol<\/th>\n                <th>Meaning<\/th>\n                <th>Use in ionic equations<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"State symbol\">(s)<\/td>\n                <td data-label=\"Meaning\">Solid<\/td>\n                <td data-label=\"Use in ionic equations\">Used for precipitates and insoluble substances.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"State symbol\">(l)<\/td>\n                <td data-label=\"Meaning\">Liquid<\/td>\n                <td data-label=\"Use in ionic equations\">Used for pure liquids, such as water.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"State symbol\">(g)<\/td>\n                <td data-label=\"Meaning\">Gas<\/td>\n                <td data-label=\"Use in ionic equations\">Used when a gaseous product forms.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"State symbol\">(aq)<\/td>\n                <td data-label=\"Meaning\">Aqueous solution<\/td>\n                <td data-label=\"Use in ionic equations\">Used for ions dissolved in water.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n        <div class=\"ols-key-box\"><p><strong>Exam tip:<\/strong> state symbols should be included in ionic equations where appropriate, especially for precipitates and aqueous ions.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Spectator Ions<\/h2><\/div>\n        <p>A <strong>spectator ion<\/strong> is an ion that is present in the reaction mixture but does not change during the reaction. It appears unchanged on both sides of the full ionic equation.<\/p>\n        <p>For example, in the reaction between sodium chloride solution and silver nitrate solution, sodium ions and nitrate ions remain dissolved in solution. They do not form the precipitate.<\/p>\n        <div class=\"ols-definition-box\"><p><strong>Spectator ion:<\/strong> an ion that is present during a reaction but is not chemically changed.<\/p><\/div>\n        <div class=\"ols-key-box\"><p><strong>How to spot one:<\/strong> if the same ion appears with the same charge and state symbol on both sides of the equation, it can be cancelled.<\/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: Spot the Spectator Ions<\/h2>\n<p>In each round, pick the one accurate statement about the ions in the reaction.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-289\" class=\"h5p-iframe\" data-content-id=\"289\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Spectator Ions Summary: Which Ions Do Not Change?\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card orange\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">4<\/div><h2>Precipitation Reactions<\/h2><\/div>\n        <p>A <strong>precipitation reaction<\/strong> occurs when two solutions are mixed and an insoluble solid forms. The solid product is called a <strong>precipitate<\/strong>.<\/p>\n        <p>Precipitation reactions are a common context for ionic equations because the useful equation often shows only the two ions that join together to form the insoluble solid.<\/p>\n        <div class=\"ols-definition-box\"><p><strong>Precipitate:<\/strong> an insoluble solid formed when two solutions react.<\/p><\/div>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Reaction mixture<\/th>\n                <th>Observation<\/th>\n                <th>Ionic change<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Reaction mixture\">Sodium chloride solution and silver nitrate solution<\/td>\n                <td data-label=\"Observation\">A white precipitate forms.<\/td>\n                <td data-label=\"Ionic change\">Ag<sup>+<\/sup>(aq) and Cl<sup>&#8211;<\/sup>(aq) form AgCl(s).<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Reaction mixture\">Barium chloride solution and sulfate ions<\/td>\n                <td data-label=\"Observation\">A white precipitate forms.<\/td>\n                <td data-label=\"Ionic change\">Ba<sup>2+<\/sup>(aq) and SO<sub>4<\/sub><sup>2-<\/sup>(aq) form BaSO<sub>4<\/sub>(s).<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n      <\/article>\n\n      <div class=\"ols-zoom-card\">\n        <div class=\"ols-zoom-card-image\">\n          <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/precipitation-reaction.webp\" alt=\"Precipitation reaction showing ions joining to form an insoluble solid\" class=\"ols-zoomable-img ols-lightbox-target\" draggable=\"false\">\n        <\/div>\n        <div class=\"ols-zoom-card-caption\">\n          <p>A precipitate forms when ions in solution are strongly attracted and produce an insoluble solid.<\/p>\n        <\/div>\n      <\/div>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">5<\/div><h2>Example: Silver Chloride Precipitation<\/h2><\/div>\n        <p>When sodium chloride solution is mixed with silver nitrate solution, a white precipitate of <strong>silver chloride<\/strong> forms.<\/p>\n        <div class=\"ols-definition-box\"><p><strong>Full equation:<\/strong> NaCl(aq) + AgNO<sub>3<\/sub>(aq) \u2192 AgCl(s) + NaNO<sub>3<\/sub>(aq)<\/p><\/div>\n        <p>In solution, the dissolved ionic compounds can be shown as ions:<\/p>\n        <div class=\"ols-definition-box\"><p>Na<sup>+<\/sup>(aq) + Cl<sup>&#8211;<\/sup>(aq) + Ag<sup>+<\/sup>(aq) + NO<sub>3<\/sub><sup>&#8211;<\/sup>(aq) \u2192 AgCl(s) + Na<sup>+<\/sup>(aq) + NO<sub>3<\/sub><sup>&#8211;<\/sup>(aq)<\/p><\/div>\n        <p>The <strong>Na<sup>+<\/sup><\/strong> and <strong>NO<sub>3<\/sub><sup>&#8211;<\/sup><\/strong> ions are spectator ions. Once they are removed, the ionic equation is:<\/p>\n        <div class=\"ols-key-box\"><p><strong>Ionic equation:<\/strong> Ag<sup>+<\/sup>(aq) + Cl<sup>&#8211;<\/sup>(aq) \u2192 AgCl(s)<\/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: Ionic Equation for a Precipitate<\/h2>\n<p>Choose the ionic equation that has the right ions, balanced charges and the right state symbol.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-636\" class=\"h5p-iframe\" data-content-id=\"636\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Ionic Equations MCQ: Iron(III) Hydroxide Precipitate\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">6<\/div><h2>How to Write Ionic Equations<\/h2><\/div>\n        <p>Start with the balanced full equation, then separate aqueous ionic substances into ions. Substances with state symbols <strong>(s)<\/strong>, <strong>(l)<\/strong> and <strong>(g)<\/strong> normally stay together.<\/p>\n        <ol>\n          <li>Write a correct balanced full equation.<\/li>\n          <li>Split aqueous ionic substances into their ions.<\/li>\n          <li>Keep solids, liquids, gases and covalent molecules together.<\/li>\n          <li>Cancel spectator ions that appear unchanged on both sides.<\/li>\n          <li>Check that atoms and charges are balanced.<\/li>\n        <\/ol>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Substance type<\/th>\n                <th>What to do<\/th>\n                <th>Example<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Substance type\">Aqueous ionic compound<\/td>\n                <td data-label=\"What to do\">Split into ions.<\/td>\n                <td data-label=\"Example\">NaCl(aq) becomes Na<sup>+<\/sup>(aq) + Cl<sup>&#8211;<\/sup>(aq)<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Substance type\">Solid precipitate<\/td>\n                <td data-label=\"What to do\">Keep as a formula.<\/td>\n                <td data-label=\"Example\">AgCl(s) stays as AgCl(s)<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Substance type\">Liquid water<\/td>\n                <td data-label=\"What to do\">Keep as a molecule.<\/td>\n                <td data-label=\"Example\">H<sub>2<\/sub>O(l) stays as H<sub>2<\/sub>O(l)<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Substance type\">Gas<\/td>\n                <td data-label=\"What to do\">Keep as a formula.<\/td>\n                <td data-label=\"Example\">H<sub>2<\/sub>(g) stays as H<sub>2<\/sub>(g)<\/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: Split or Keep Together?<\/h2>\n<p>Click every substance that is written as separate ions in an ionic equation.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-637\" class=\"h5p-iframe\" data-content-id=\"637\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Ionic Equations Mark the Words: Which Substances Are Split into Ions?\"><\/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>Example: Barium Sulfate Precipitation<\/h2><\/div>\n        <p>When barium chloride solution is added to a solution containing sulfate ions, a white precipitate of <strong>barium sulfate<\/strong> forms.<\/p>\n        <div class=\"ols-definition-box\"><p><strong>Full equation:<\/strong> BaCl<sub>2<\/sub>(aq) + MgSO<sub>4<\/sub>(aq) \u2192 BaSO<sub>4<\/sub>(s) + MgCl<sub>2<\/sub>(aq)<\/p><\/div>\n        <p>The ions that form the insoluble precipitate are <strong>Ba<sup>2+<\/sup><\/strong> and <strong>SO<sub>4<\/sub><sup>2-<\/sup><\/strong>.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Ionic equation:<\/strong> Ba<sup>2+<\/sup>(aq) + SO<sub>4<\/sub><sup>2-<\/sup>(aq) \u2192 BaSO<sub>4<\/sub>(s)<\/p><\/div>\n        <p>This reaction is used as a chemical test for sulfate ions. The sample is usually acidified before barium chloride solution is added.<\/p>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">8<\/div><h2>Ionic Equations Beyond Precipitation<\/h2><\/div>\n        <p>Ionic equations are also useful for displacement reactions because they show the species that gain or lose electrons, or the ions that are displaced.<\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Reaction type<\/th>\n                <th>Example full equation<\/th>\n                <th>Useful ionic equation<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Reaction type\">Metal displacement<\/td>\n                <td data-label=\"Example full equation\">Mg(s) + CuSO<sub>4<\/sub>(aq) \u2192 MgSO<sub>4<\/sub>(aq) + Cu(s)<\/td>\n                <td data-label=\"Useful ionic equation\">Mg(s) + Cu<sup>2+<\/sup>(aq) \u2192 Mg<sup>2+<\/sup>(aq) + Cu(s)<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Reaction type\">Halogen displacement<\/td>\n                <td data-label=\"Example full equation\">Cl<sub>2<\/sub>(aq) + 2KBr(aq) \u2192 2KCl(aq) + Br<sub>2<\/sub>(aq)<\/td>\n                <td data-label=\"Useful ionic equation\">Cl<sub>2<\/sub>(aq) + 2Br<sup>&#8211;<\/sup>(aq) \u2192 2Cl<sup>&#8211;<\/sup>(aq) + Br<sub>2<\/sub>(aq)<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n        <div class=\"ols-key-box\"><p><strong>Exam tip:<\/strong> spectator ions are not always sodium, potassium or nitrate ions, but these are very common because their compounds are usually soluble.<\/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: Atoms Balance, but Does the Charge?<\/h2>\n<p>Decide whether the ionic equation for this displacement reaction is balanced.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-638\" class=\"h5p-iframe\" data-content-id=\"638\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Ionic Equations True or False: Is the Charge Balanced?\"><\/iframe><\/div><\/div>\n<\/section>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Write the Ionic Equations<\/h2>\n<p>Write the full and ionic equations on paper before you flip each card.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-639\" class=\"h5p-iframe\" data-content-id=\"639\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Ionic Equations Flip Cards: New Precipitation and Displacement Reactions\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">9<\/div><h2>Common Exam Points<\/h2><\/div>\n        <ul>\n          <li>Ionic equations show only the particles that actually change.<\/li>\n          <li>Spectator ions appear unchanged on both sides of the equation and are cancelled.<\/li>\n          <li>The state symbol (aq) means aqueous, which means dissolved in water.<\/li>\n          <li>Precipitation reactions form an insoluble solid from ions in solution.<\/li>\n          <li>For precipitation reactions, the precipitate is written as a solid with the state symbol (s).<\/li>\n          <li>Do not split solids, liquids, gases or covalent molecules into ions.<\/li>\n          <li>Always check that the final ionic equation is balanced for both atoms and charge.<\/li>\n          <li>Ag<sup>+<\/sup>(aq) + Cl<sup>&#8211;<\/sup>(aq) \u2192 AgCl(s) is the ionic equation for forming silver chloride.<\/li>\n          <li>Ba<sup>2+<\/sup>(aq) + SO<sub>4<\/sub><sup>2-<\/sup>(aq) \u2192 BaSO<sub>4<\/sub>(s) is the ionic equation for forming barium sulfate.<\/li>\n        <\/ul>\n      <\/article>\n\n      \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>Ionic equations:<\/strong> show the particles that actually react.<\/li>\n          <li><strong>Spectator ions:<\/strong> ions that appear unchanged on both sides of the equation.<\/li>\n          <li><strong>Aqueous ions:<\/strong> ions in solution are shown using the state symbol (aq).<\/li>\n          <li><strong>Precipitation:<\/strong> two aqueous ions combine to form an insoluble solid.<\/li>\n          <li><strong>Silver chloride:<\/strong> Ag<sup>+<\/sup>(aq) + Cl<sup>&#8211;<\/sup>(aq) \u2192 AgCl(s).<\/li>\n          <li><strong>Barium sulfate:<\/strong> Ba<sup>2+<\/sup>(aq) + SO<sub>4<\/sub><sup>2-<\/sup>(aq) \u2192 BaSO<sub>4<\/sub>(s).<\/li>\n          <li><strong>Final check:<\/strong> atoms and overall charge must both balance.<\/li>\n        <\/ul>\n      <\/section>\n\n      <div class=\"ols-image-lightbox\" id=\"olsImageLightboxIonicEquations001\" aria-hidden=\"true\" role=\"dialog\" aria-modal=\"true\" aria-label=\"Expanded revision image\">\n        <div class=\"ols-image-lightbox-inner\">\n          <button class=\"ols-image-lightbox-close\" type=\"button\" aria-label=\"Close enlarged image\">\u00d7<\/button>\n          <img decoding=\"async\" class=\"ols-image-lightbox-img\" src=\"\" alt=\"\">\n        <\/div>\n      <\/div>\n\n      <script>\n        (function(){\n          var page = document.querySelector(\".ols-ionic-equations-page\");\n          if (!page) {\n            return;\n          }\n\n          var lightbox = 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3.1.2 Amount of Substance course page\">\r\n\r\n        <div class=\"ols-course-cta-image\">\r\n          <img decoding=\"async\"\r\n            src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/06\/3-1-2-Amount-of-Substance.jpg\"\r\n            alt=\"AQA A Level Chemistry 3.1.2 Amount of Substance interactive course banner\"\r\n          >\r\n        <\/div>\r\n\r\n      <\/a>\r\n\r\n      <div class=\"ols-course-cta-content\">\r\n\r\n        <div class=\"ols-course-cta-header-row\">\r\n\r\n          <div class=\"ols-course-cta-kicker\">AQA 7405<\/div>\r\n          <div class=\"ols-course-cta-kicker\">Paper 1 &amp; Paper 2<\/div>\r\n          <div class=\"ols-course-cta-kicker\">3.1.2 Amount of Substance<\/div>\r\n\r\n        <\/div>\r\n\r\n        <h2>\r\n          Master Amount of Substance for AQA A Level Chemistry\r\n        <\/h2>\r\n\r\n        <div class=\"ols-course-cta-heading-button\">\r\n          <a\r\n            class=\"ols-course-button ols-course-button-top\"\r\n            href=\"[insert here]\">\r\n            View Course\r\n          <\/a>\r\n        <\/div>\r\n\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-intro-stats\">\r\n\r\n      <p class=\"ols-course-cta-intro\">\r\n        Continue from these free revision notes into the full 3.1.2 Amount of Substance course, covering moles, Avogadro constant, empirical and molecular formulae, reacting masses, concentration, titrations, gas volumes, percentage yield and atom economy with guided video teaching, diagnostic MCQ practice, teacher-marked short-answer questions and a personalised progress report.\r\n      <\/p>\r\n\r\n      <div class=\"ols-course-cta-stats\">\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Guided learning<\/span>\r\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Video lessons<\/span>\r\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>MCQ practice<\/span>\r\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>SAQ practice<\/span>\r\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-features\">\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Guided video teaching<\/h3>\r\n        <p>\r\n          Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Instant MCQ feedback<\/h3>\r\n        <p>\r\n          Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Teacher-marked SAQs<\/h3>\r\n        <p>\r\n          Submit written exam responses and receive chemistry specialist feedback with improvement guidance.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Progress tracking<\/h3>\r\n        <p>\r\n          Identify strengths and weaknesses across the full 3.1.2 Amount of Substance specification, including mole calculations, formulae, solution calculations, gas calculations, yield and atom economy.\r\n        <\/p>\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-animation-wrap\">\r\n\r\n      <h3 class=\"ols-course-animation-title\">\r\n        See how the course works\r\n      <\/h3>\r\n\r\n      <div class=\"ols-animation-frame-shell\">\r\n        <iframe\r\n          id=\"olsCourseAnimationFrame312\"\r\n          title=\"OLS course preview animation\"\r\n          loading=\"lazy\"\r\n          referrerpolicy=\"no-referrer\">\r\n        <\/iframe>\r\n\r\n        <button\r\n          class=\"ols-animation-start-overlay\"\r\n          id=\"olsCourseAnimationStart312\"\r\n          type=\"button\"\r\n          aria-label=\"Play OLS course preview animation\">\r\n          <span class=\"ols-animation-start-content\">\r\n            <span class=\"ols-animation-play-circle\" aria-hidden=\"true\">\r\n              <span class=\"ols-animation-play-icon\"><\/span>\r\n            <\/span>\r\n            <span class=\"ols-animation-start-text\">\r\n              Play course preview animation\r\n            <\/span>\r\n          <\/span>\r\n        <\/button>\r\n\r\n        <button\r\n          class=\"ols-animation-pause-button\"\r\n          id=\"olsCourseAnimationPause312\"\r\n          type=\"button\"\r\n          aria-label=\"Pause course preview animation\">\r\n          Pause\r\n        <\/button>\r\n      <\/div>\r\n\r\n      <p class=\"ols-course-video-status\">\r\n        Click play to start the course preview animation.\r\n      <\/p>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-bottom\">\r\n\r\n      <a\r\n        class=\"ols-course-button\"\r\n        href=\"[insert here]\">\r\n        View Course\r\n      <\/a>\r\n\r\n    <\/div>\r\n\r\n  <\/div>\r\n\r\n  <template id=\"olsCourseAnimationTemplate312\">\r\n<!DOCTYPE html>\r\n<html lang=\"en\">\r\n<head>\r\n<meta charset=\"UTF-8\">\r\n<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">\r\n<title>OLS Amount of Substance Promo Animation<\/title>\r\n\r\n<style>\r\n*{box-sizing:border-box;}\r\n\r\nhtml.ols-animation-paused *,\r\nhtml.ols-animation-paused *::before,\r\nhtml.ols-animation-paused *::after{\r\n  animation-play-state:paused!important;\r\n}\r\n\r\n:root{\r\n  --ols-video-screen-w:1180;\r\n  --ols-video-screen-h:664;\r\n  --ols-video-screen-scale:1;\r\n  --ols-mcq-screen-w:1360;\r\n  --ols-mcq-screen-h:1130;\r\n  --ols-mcq-screen-scale:1;\r\n  --ols-saq-screen-w:1360;\r\n  --ols-saq-screen-h:965;\r\n  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white-space:pre-wrap;\r\n}\r\n\r\n.mcq-specific-cursor{background:#111827;}\r\n.mcq-general-cursor{background:#8a6a00;}\r\n\r\n.ols-saq-screen{\r\n  width:1360px;\r\n  height:965px;\r\n  border-radius:22px;\r\n  overflow:hidden;\r\n  background:#eaf0ff;\r\n  box-shadow:0 26px 70px rgba(28,36,75,0.22);\r\n  opacity:0;\r\n  transform:translateY(24px) scale(0.96);\r\n}\r\n\r\n.ols-saq-screen.show{\r\n  animation:olsSaqScreenEnter 1s ease forwards;\r\n}\r\n\r\n@keyframes olsSaqScreenEnter{\r\n  from{opacity:0;transform:translateY(24px) scale(0.96);}\r\n  to{opacity:1;transform:translateY(0) scale(1);}\r\n}\r\n\r\n.saq-question-area{\r\n  height:335px;\r\n  background:#eaf0ff;\r\n  padding:30px 40px 32px;\r\n}\r\n\r\n.saq-question-text{\r\n  font-size:25px;\r\n  line-height:1.42;\r\n  color:#111827;\r\n  margin-bottom:22px;\r\n}\r\n\r\n.saq-student-box{\r\n  height:195px;\r\n  background:#f3f4f6;\r\n  border:2px solid #cfd6e3;\r\n  border-radius:8px;\r\n  padding:23px 26px;\r\n  font-size:24px;\r\n  line-height:1.55;\r\n  color:#4b5563;\r\n  position:relative;\r\n  overflow:hidden;\r\n}\r\n\r\n.saq-teacher-feedback{\r\n  height:630px;\r\n  background:#dff3e6;\r\n  color:#075f3b;\r\n  padding:28px 40px 30px;\r\n  font-size:23px;\r\n  line-height:1.47;\r\n  opacity:0;\r\n  transform:translateY(20px);\r\n  transition:opacity 0.7s ease,transform 0.7s ease;\r\n  overflow:hidden;\r\n}\r\n\r\n.saq-teacher-feedback.show{\r\n  opacity:1;\r\n  transform:translateY(0);\r\n}\r\n\r\n#saqTeacherText{\r\n  white-space:pre-wrap;\r\n}\r\n\r\n.saq-teacher-cursor{\r\n  background:#075f3b;\r\n}\r\n\r\n@media(max-width:900px){\r\n  .ols-video-title,\r\n  .ols-mcq-intro-title,\r\n  .ols-saq-intro-title{\r\n    font-size:clamp(42px,11vw,78px);\r\n    line-height:1.12;\r\n  }\r\n\r\n  .ols-title-cursor{\r\n    width:4px;\r\n    margin-left:6px;\r\n  }\r\n\r\n  .ols-video-card{\r\n    border-radius:20px;\r\n  }\r\n}\r\n<\/style>\r\n<\/head>\r\n\r\n<body>\r\n<div class=\"ols-combined-stage\">\r\n\r\n  <section id=\"sceneVideo\" class=\"ols-scene active\">\r\n    <div class=\"ols-video-stage\">\r\n      <div id=\"videoTitleScreen\" class=\"ols-video-title-screen\">\r\n        <div class=\"ols-video-title-wrap\">\r\n          <h1 class=\"ols-video-title\">\r\n            <span id=\"videoTitleText\"><\/span><span id=\"videoTitleCursor\" class=\"ols-title-cursor\"><\/span>\r\n          <\/h1>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <section id=\"videoScene\" class=\"ols-video-scene\">\r\n        <div class=\"ols-video-scale-wrap\">\r\n          <div class=\"ols-video-card\">\r\n            <video\r\n              id=\"lessonVideo\"\r\n              src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Virtual-Lesson.mp4\"\r\n              muted\r\n              playsinline\r\n              preload=\"auto\">\r\n            <\/video>\r\n          <\/div>\r\n        <\/div>\r\n      <\/section>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section id=\"sceneMcq\" class=\"ols-scene\">\r\n    <div class=\"ols-mcq-stage\">\r\n      <div id=\"mcqIntroScreen\" class=\"ols-mcq-intro-screen\">\r\n        <div class=\"ols-mcq-intro-title-wrap\">\r\n          <h1 class=\"ols-mcq-intro-title\">\r\n            <span id=\"mcqIntroTitleText\"><\/span><span id=\"mcqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\r\n          <\/h1>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"ols-mcq-scale-wrap\">\r\n        <main id=\"mcqScreen\" class=\"ols-mcq-screen\">\r\n          <section class=\"mcq-question-area\">\r\n            <p class=\"mcq-question-lead\">A student prepares a sodium hydroxide solution.<\/p>\r\n\r\n            <table class=\"mcq-ionic-table\">\r\n              <thead>\r\n                <tr>\r\n                  <th>Quantity<\/th>\r\n                  <th>Value<\/th>\r\n                <\/tr>\r\n              <\/thead>\r\n              <tbody>\r\n                <tr><td>Concentration of NaOH<\/td><td>0.200 mol dm<sup>\u22123<\/sup><\/td><\/tr>\r\n                <tr><td>Volume used<\/td><td>25.0 cm<sup>3<\/sup><\/td><\/tr>\r\n                <tr><td>Volume in dm<sup>3<\/sup><\/td><td>0.0250 dm<sup>3<\/sup><\/td><\/tr>\r\n              <\/tbody>\r\n            <\/table>\r\n\r\n            <p class=\"mcq-question-main\">What amount of NaOH is present in the 25.0 cm<sup>3<\/sup> sample?<\/p>\r\n\r\n            <div class=\"mcq-options-wrap\">\r\n              <div id=\"mcqWrongOption\" class=\"mcq-option-row\">\r\n                <span class=\"mcq-radio\"><\/span>\r\n                <span class=\"mcq-radio-ripple\"><\/span>\r\n                <span class=\"mcq-option-label\">5.00 mol<\/span>\r\n\r\n                <span id=\"mcqSpecificFeedback\" class=\"mcq-specific-feedback\">\r\n                  <span id=\"mcqCrossIcon\" class=\"mcq-cross-icon\">\u00d7<\/span>\r\n                  <span class=\"mcq-specific-feedback-text\">\r\n                    <span id=\"mcqSpecificText\"><\/span><span id=\"mcqSpecificCursor\" class=\"cursor mcq-specific-cursor\" style=\"display:none;\"><\/span>\r\n                  <\/span>\r\n                <\/span>\r\n              <\/div>\r\n\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">0.500 mol<\/span><\/div>\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">0.00500 mol<\/span><\/div>\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">0.000500 mol<\/span><\/div>\r\n            <\/div>\r\n\r\n            <button id=\"mcqSubmitButton\" class=\"mcq-submit-button\">Submit answer<\/button>\r\n          <\/section>\r\n\r\n          <section id=\"mcqGeneralFeedback\" class=\"mcq-general-feedback\">\r\n            <span id=\"mcqGeneralText\"><\/span><span id=\"mcqGeneralCursor\" class=\"cursor mcq-general-cursor\" style=\"display:none;\"><\/span>\r\n          <\/section>\r\n        <\/main>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section id=\"sceneSaq\" class=\"ols-scene\">\r\n    <div class=\"ols-saq-stage\">\r\n      <div id=\"saqIntro\" class=\"ols-saq-intro\">\r\n        <div class=\"ols-saq-intro-title-wrap\">\r\n          <h1 class=\"ols-saq-intro-title\">\r\n            <span id=\"saqIntroTitleText\"><\/span><span id=\"saqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\r\n          <\/h1>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"ols-saq-scale-wrap\">\r\n        <main id=\"saqScreen\" class=\"ols-saq-screen\">\r\n          <section class=\"saq-question-area\">\r\n            <div class=\"saq-question-text\">\r\n              <strong>(ii)<\/strong>&nbsp;&nbsp; Calcium carbonate reacts with hydrochloric acid.<br>\r\n              Calculate the mass of CaCO<sub>3<\/sub> that reacts with 25.0 cm<sup>3<\/sup> of 0.200 mol dm<sup>\u22123<\/sup> HCl.<br>\r\n              CaCO<sub>3<\/sub> + 2HCl \u2192 CaCl<sub>2<\/sub> + H<sub>2<\/sub>O + CO<sub>2<\/sub>\r\n            <\/div>\r\n\r\n            <div class=\"saq-student-box\">\r\n              <span id=\"saqStudentText\"><\/span><span id=\"saqStudentCursor\" class=\"cursor\"><\/span>\r\n            <\/div>\r\n          <\/section>\r\n\r\n          <section id=\"saqTeacherFeedback\" class=\"saq-teacher-feedback\">\r\n            <span id=\"saqTeacherText\"><\/span><span id=\"saqTeacherCursor\" class=\"cursor saq-teacher-cursor\" style=\"display:none;\"><\/span>\r\n          <\/section>\r\n        <\/main>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n<\/div>\r\n\r\n<script>\r\n(function(){\r\n  const nativeSetTimeout=window.setTimeout.bind(window);\r\n  const nativeClearTimeout=window.clearTimeout.bind(window);\r\n  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Convert cm\u00b3 to dm\u00b3 before multiplying by concentration.\";\r\nconst mcqGeneralFeedbackText=\r\n\"Your answer is incorrect.\\n\\n\"+\r\n\"For solution concentration calculations, always convert the volume into dm\u00b3 before using n = cV.\\n\\n\"+\r\n\"\u2022 Volume = 25.0 cm\u00b3 = 25.0 \u00f7 1000 = 0.0250 dm\u00b3.\\n\"+\r\n\"\u2022 Concentration = 0.200 mol dm\u207b\u00b3.\\n\"+\r\n\"\u2022 Amount = concentration \u00d7 volume.\\n\"+\r\n\"\u2022 n = 0.200 \u00d7 0.0250 = 0.00500 mol.\\n\\n\"+\r\n\"The correct answer is: 0.00500 mol\";\r\n\r\nconst mcqIntroScreen=document.getElementById(\"mcqIntroScreen\");\r\nconst mcqIntroTitleText=document.getElementById(\"mcqIntroTitleText\");\r\nconst mcqIntroTitleCursor=document.getElementById(\"mcqIntroTitleCursor\");\r\nconst mcqScreen=document.getElementById(\"mcqScreen\");\r\nconst mcqWrongOption=document.getElementById(\"mcqWrongOption\");\r\nconst mcqSubmitButton=document.getElementById(\"mcqSubmitButton\");\r\nconst mcqSpecificFeedback=document.getElementById(\"mcqSpecificFeedback\");\r\nconst mcqCrossIcon=document.getElementById(\"mcqCrossIcon\");\r\nconst mcqSpecificText=document.getElementById(\"mcqSpecificText\");\r\nconst mcqSpecificCursor=document.getElementById(\"mcqSpecificCursor\");\r\nconst mcqGeneralFeedback=document.getElementById(\"mcqGeneralFeedback\");\r\nconst mcqGeneralText=document.getElementById(\"mcqGeneralText\");\r\nconst mcqGeneralCursor=document.getElementById(\"mcqGeneralCursor\");\r\n\r\nfunction selectMcqWrongOption(){\r\n  mcqWrongOption.classList.add(\"clicking\");\r\n\r\n  setTimeout(function(){\r\n    mcqWrongOption.classList.add(\"selected\");\r\n  },220);\r\n\r\n  setTimeout(function(){\r\n    mcqWrongOption.classList.remove(\"clicking\");\r\n  },850);\r\n}\r\n\r\nfunction clickMcqSubmit(){\r\n  mcqSubmitButton.classList.add(\"clicked\");\r\n\r\n  setTimeout(function(){\r\n    mcqSubmitButton.classList.remove(\"clicked\");\r\n  },240);\r\n}\r\n\r\nfunction showMcqSpecificFeedback(){\r\n  mcqSpecificFeedback.classList.add(\"show\");\r\n\r\n  setTimeout(function(){\r\n    mcqCrossIcon.classList.add(\"show\");\r\n  },180);\r\n\r\n  setTimeout(function(){\r\n    mcqSpecificCursor.style.display=\"inline-block\";\r\n\r\n    typeWriter(mcqSpecificText,mcqSpecificFeedbackText,12,function(){\r\n      mcqSpecificCursor.style.display=\"none\";\r\n\r\n      setTimeout(function(){\r\n        showMcqGeneralFeedback();\r\n      },650);\r\n    });\r\n  },560);\r\n}\r\n\r\nfunction showMcqGeneralFeedback(){\r\n  mcqGeneralFeedback.classList.add(\"show\");\r\n\r\n  setTimeout(function(){\r\n    mcqGeneralCursor.style.display=\"inline-block\";\r\n\r\n    typeWriter(mcqGeneralText,mcqGeneralFeedbackText,8,function(){\r\n      mcqGeneralCursor.style.display=\"none\";\r\n\r\n      setTimeout(function(){\r\n        switchScene(sceneMcq,sceneSaq,function(){\r\n          startSaqIntro();\r\n        });\r\n      },2600);\r\n    });\r\n  },600);\r\n}\r\n\r\nfunction startMcqAnimation(){\r\n  fitMcqScreen();\r\n  mcqScreen.classList.add(\"show\");\r\n\r\n  setTimeout(function(){\r\n    selectMcqWrongOption();\r\n\r\n    setTimeout(function(){\r\n      clickMcqSubmit();\r\n\r\n      setTimeout(function(){\r\n        showMcqSpecificFeedback();\r\n      },620);\r\n    },1150);\r\n  },1300);\r\n}\r\n\r\nfunction startMcqIntro(){\r\n  fitMcqScreen();\r\n\r\n  setTimeout(function(){\r\n    typeWriter(mcqIntroTitleText,mcqIntroTitle,44,function(){\r\n      setTimeout(function(){\r\n        mcqIntroTitleCursor.style.display=\"none\";\r\n\r\n        setTimeout(function(){\r\n          mcqIntroScreen.classList.add(\"hide\");\r\n\r\n          setTimeout(function(){\r\n            startMcqAnimation();\r\n          },850);\r\n        },3000);\r\n      },250);\r\n    });\r\n  },700);\r\n}\r\n\r\nconst saqIntroTitle=\"Chemistry Specialist\\nMarked Exam Feedback\";\r\nconst saqStudentAnswer=\"Moles of HCl = 0.200 \u00d7 0.0250 = 0.00500 mol. The mass of calcium carbonate is 0.00500 \u00d7 100 = 0.500 g.\";\r\nconst saqTeacherFeedbackText=\r\n\"Comment:\\n\"+\r\n\"Your first step is correct: you converted 25.0 cm\u00b3 to 0.0250 dm\u00b3 and calculated 0.00500 mol of HCl. The error is that you did not use the mole ratio in the balanced equation.\\n\\n\"+\r\n\"The equation shows that 1 mol of CaCO\u2083 reacts with 2 mol of HCl. Therefore the amount of CaCO\u2083 is half the amount of HCl.\\n\\n\"+\r\n\"Correct method:\\n\"+\r\n\"\u2022 n(HCl) = cV = 0.200 \u00d7 0.0250 = 0.00500 mol \u2713\\n\"+\r\n\"\u2022 n(CaCO\u2083) = 0.00500 \u00f7 2 = 0.00250 mol \u2713\\n\"+\r\n\"\u2022 M\u1d63(CaCO\u2083) = 40.1 + 12.0 + (3 \u00d7 16.0) = 100.1 \u2713\\n\"+\r\n\"\u2022 mass = n \u00d7 M\u1d63 = 0.00250 \u00d7 100.1 = 0.250 g \u2713\\n\\n\"+\r\n\"Next time, always use the balanced equation after calculating moles. 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Spectator ions are removed because they do not change.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>What is a spectator ion?<\/h3>\n            <p>A spectator ion is an ion that remains unchanged during a reaction. It appears on both sides of the full ionic equation with the same charge and state symbol.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why do precipitates form?<\/h3>\n            <p>A precipitate forms when ions in solution combine to make an insoluble solid. For example, Ag<sup>+<\/sup>(aq) and Cl<sup>&#8211;<\/sup>(aq) form AgCl(s).<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Do I split every compound into ions?<\/h3>\n            <p>No. Only aqueous ionic substances are split into ions. Solids, liquids, gases and covalent molecules are normally kept together.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>How do I check my ionic equation is correct?<\/h3>\n            <p>Check that the atoms balance and that the total charge on the left equals the total charge on the right. A chemically correct ionic equation must satisfy both checks.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-related-card\">\n        <h2>Related Topics<\/h2>\n        <p>Build the surrounding skills needed to write and interpret ionic equations confidently.<\/p>\n        <div class=\"ols-related-grid\">\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/writing-chemical-equations\/\">Writing Chemical Equations<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/\">Chemical Equations and Reacting Masses<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/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\/aqa\/3-1-2-amount-of-substance\/the-mole-and-avogadro-constant\/\">The Mole and Avogadro Constant<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/relative-masses\/\">Relative Masses<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/\">3.1.2 Amount of Substance<\/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\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/ionic-equations\/#webpage\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/chemical-equations-and-reacting-masses\/ionic-equations\/\",\n            \"name\": \"Ionic Equations - AQA A Level Chemistry\",\n            \"description\": \"AQA A Level Chemistry revision notes covering ionic equations, spectator ions, state symbols, precipitation reactions and charge balancing.\",\n            \"inLanguage\": \"en-GB\",\n            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Ionic equations show the reacting particles after unchanged spectator ions have been removed. 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