{"id":5277,"date":"2026-06-19T04:55:05","date_gmt":"2026-06-19T03:55:05","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/empirical-and-molecular-formulae\/molecular-formula\/"},"modified":"2026-09-19T20:36:24","modified_gmt":"2026-09-19T19:36:24","slug":"molecular-formula","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/empirical-and-molecular-formulae\/molecular-formula\/","title":{"rendered":"Molecular Formula"},"content":{"rendered":"\n<!--\n===============================================================================\nONLINE LEARNING SYSTEM COPYRIGHT NOTICE\n\u00a9 Online Learning System. All rights reserved.\n\nThis WordPress revision page HTML, CSS, content sequence, educational wording,\nlayout structure, schema structure and embedded design logic are protected\nintellectual property of Online Learning System.\n\nUnauthorised copying, redistribution, resale, modification, republication,\nscraping, extraction, derivative reuse, automated harvesting or removal of\ncopyright notices is strictly prohibited.\n\nBackend copyright marker:\nOLS-AQA-312-MOLECULAR-FORMULA-REVISION-PAGE-7405-2026\n\nPage:\nMolecular Formula\nAQA A Level Chemistry\nPaper 1 and Paper 2\n3.1.2 Amount of Substance\n7405\/1 and 7405\/2\n\nCopyright enforcement notes:\n- The visible student page is a free OLS revision resource.\n- The backend HTML structure, CSS architecture, card sequencing, schema graph,\n  revision wording, responsive table behaviour and embedded learning pathway are\n  proprietary OLS production assets.\n- Do not remove this notice.\n===============================================================================\n-->\n\n<section class=\"ols-revision-page ols-molecular-formula-page\" data-owner=\"Online Learning System\" data-copyright=\"\u00a9 Online Learning System. 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OLS protected content block.\n    Page: Molecular Formula.\n    This content is authored for Online Learning System and must not be scraped,\n    cloned, republished, resold, reformatted into derivative notes, or reused in\n    competing resources without written permission.\n  -->\n\n  <div class=\"ols-revision-layout\">\n    <aside class=\"ols-sidebar\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>AQA A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>3.1.2 Amount of Substance<\/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\/3-1-2-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      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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\/empirical-and-molecular-formulae\/\">Empirical and Molecular Formulae<\/a> \/\n        <span>Molecular Formula<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Molecular Formula<\/h1>\n        <p class=\"ols-page-intro\">A focused revision guide to molecular formulae for AQA A Level Chemistry. This page shows how to convert empirical formulae into molecular formulae using relative molecular mass, percentage composition and worked examples.<\/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: 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>What Is a Molecular Formula?<\/h2><\/div>\n        <p>The <strong>molecular formula<\/strong> shows the number of atoms of each element in one molecule of a compound. It gives more information than an empirical formula because it gives the atom count in the molecule, not just the simplest ratio.<\/p>\n        <p>For example, the empirical formula of glucose is CH<sub>2<\/sub>O, but the molecular formula is <strong>C<sub>6<\/sub>H<sub>12<\/sub>O<sub>6<\/sub><\/strong>. The molecular formula is six times the empirical formula.<\/p>\n        <div class=\"ols-definition-box\">\n          <p><strong>Definition:<\/strong> A molecular formula shows the <strong>number of atoms of each element<\/strong> in one molecule of the compound.<\/p>\n        <\/div>\n        <div class=\"ols-key-box\">\n          <p><strong>Key distinction:<\/strong> an empirical formula gives the simplest ratio, while a molecular formula gives the molecular formula of a molecule.<\/p>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Molecular or Already Simplest?<\/h2>\n<p>Click every molecular formula that is the same as its empirical formula.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-643\" class=\"h5p-iframe\" data-content-id=\"643\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Molecular Formula Mark the Words: Already the Simplest Ratio\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>The Core Relationship<\/h2><\/div>\n        <p>To find a molecular formula from an empirical formula, compare the relative molecular mass of the whole compound with the relative formula mass of the empirical formula.<\/p>\n        <div class=\"ols-definition-box\">\n          <p><strong>n = M<sub>r<\/sub> of compound \u00f7 M<sub>r<\/sub> of empirical formula<\/strong><\/p>\n        <\/div>\n        <p>Then multiply every subscript in the empirical formula by <strong>n<\/strong>. The value of n should be a whole number because a molecule contains a whole-number multiple of the empirical formula.<\/p>\n        <div class=\"ols-rule-list\">\n          <div class=\"ols-rule-item\">\n            <h3>Step 1 \u2014 Find the M<sub>r<\/sub> of the empirical formula<\/h3>\n            <p>Add the relative atomic masses for one empirical formula.<\/p>\n          <\/div>\n          <div class=\"ols-rule-item\">\n            <h3>Step 2 \u2014 Divide the compound M<sub>r<\/sub> by the empirical formula M<sub>r<\/sub><\/h3>\n            <p>This gives the multiplier, n.<\/p>\n          <\/div>\n          <div class=\"ols-rule-item\">\n            <h3>Step 3 \u2014 Multiply the empirical formula by n<\/h3>\n            <p>Multiply every element subscript by the same multiplier to get the molecular formula.<\/p>\n          <\/div>\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\/How-to-convert-empirical-to-molecular-formula.webp\" alt=\"How to convert an empirical formula into a molecular formula using relative molecular mass\" class=\"ols-zoomable-img ols-lightbox-target\" draggable=\"false\">\n        <\/div>\n        <div class=\"ols-zoom-card-caption\">\n          <p>The molecular formula is found by checking how many times the empirical formula mass fits into the relative molecular mass of the compound.<\/p>\n        <\/div>\n      <\/div>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Worked Example: Empirical Formula Given<\/h2><\/div>\n        <p>Determine the molecular formula of a compound with empirical formula <strong>C<sub>3<\/sub>H<sub>6<\/sub>O<\/strong> and M<sub>r<\/sub> = <strong>116<\/strong>.<\/p>\n\n        <div class=\"ols-worked-example\">\n          <h3>Step 1 \u2014 Find the M<sub>r<\/sub> of the empirical formula<\/h3>\n          <div class=\"ols-calc-row\">\n            <div class=\"ols-calc-cell\"><span>C<sub>3<\/sub><\/span>3 \u00d7 12 = <strong>36<\/strong><\/div>\n            <div class=\"ols-calc-cell\"><span>H<sub>6<\/sub><\/span>6 \u00d7 1 = <strong>6<\/strong><\/div>\n            <div class=\"ols-calc-cell\"><span>O<\/span>1 \u00d7 16 = <strong>16<\/strong><\/div>\n          <\/div>\n          <p>M<sub>r<\/sub> of C<sub>3<\/sub>H<sub>6<\/sub>O = 36 + 6 + 16 = <strong>58<\/strong>.<\/p>\n        <\/div>\n\n        <div class=\"ols-worked-example\">\n          <h3>Step 2 \u2014 Find the multiplier<\/h3>\n          <p>n = 116 \u00f7 58 = <strong>2<\/strong>.<\/p>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Molecular formula: C<sub>6<\/sub>H<sub>12<\/sub>O<sub>2<\/sub><\/strong>. The empirical formula C<sub>3<\/sub>H<sub>6<\/sub>O has been multiplied by 2.<\/p>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: From Empirical to Molecular Formula<\/h2>\n<p>Find n on paper, then type the molecular formula.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-314\" class=\"h5p-iframe\" data-content-id=\"314\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Molecular Formula Flashcards: From Empirical Formula and Mr\"><\/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>Shortcut Method from Percentage Composition<\/h2><\/div>\n        <p>If you are given percentage composition and the relative molecular mass of the compound, you can find the molecular formula directly. Instead of first writing the empirical formula, find the mass of each element in one mole of the compound.<\/p>\n        <p>For a compound with M<sub>r<\/sub> = 46 containing <strong>52.2% C<\/strong>, <strong>13.0% H<\/strong> and <strong>34.8% O<\/strong>, the percentage tells you what fraction of the 46 g mol<sup>-1<\/sup> belongs to each element.<\/p>\n\n        <div class=\"ols-worked-example\">\n          <h3>Step 1 \u2014 Find the mass of each element in one mole<\/h3>\n          <div class=\"ols-calc-row\">\n            <div class=\"ols-calc-cell\"><span>Carbon<\/span>52.2% of 46 = <strong>24.01 g<\/strong><\/div>\n            <div class=\"ols-calc-cell\"><span>Hydrogen<\/span>13.0% of 46 = <strong>5.98 g<\/strong><\/div>\n            <div class=\"ols-calc-cell\"><span>Oxygen<\/span>34.8% of 46 = <strong>16.01 g<\/strong><\/div>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-worked-example\">\n          <h3>Step 2 \u2014 Convert each mass into moles of atoms<\/h3>\n          <div class=\"ols-calc-row\">\n            <div class=\"ols-calc-cell\"><span>C<\/span>24.01 \u00f7 12 \u2248 <strong>2<\/strong><\/div>\n            <div class=\"ols-calc-cell\"><span>H<\/span>5.98 \u00f7 1 \u2248 <strong>6<\/strong><\/div>\n            <div class=\"ols-calc-cell\"><span>O<\/span>16.01 \u00f7 16 \u2248 <strong>1<\/strong><\/div>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Molecular formula: C<sub>2<\/sub>H<sub>6<\/sub>O<\/strong>. This shortcut works because the percentage composition is applied to one mole of compound.<\/p>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Use the Shortcut Method<\/h2>\n<p>Find the molecular formula directly from the percentage composition and the relative molecular mass.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-328\" class=\"h5p-iframe\" data-content-id=\"328\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Molecular Formula MCQ: From Percentage Composition and Mr\"><\/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>When the M<sub>r<\/sub> Is Not Exact<\/h2><\/div>\n        <p>The relative molecular mass does not always need to match perfectly because experimental data may contain rounding. The important point is that the molecular formula must be a <strong>whole-number multiple<\/strong> of the empirical formula.<\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Calculation<\/th>\n                <th>Likely value of n<\/th>\n                <th>Exam decision<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Calculation\">119.8 \u00f7 60 = 1.997<\/td>\n                <td data-label=\"Likely value of n\">2<\/td>\n                <td data-label=\"Exam decision\">Round to 2 because the value is extremely close to a whole number.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Calculation\">178.9 \u00f7 30 = 5.963<\/td>\n                <td data-label=\"Likely value of n\">6<\/td>\n                <td data-label=\"Exam decision\">Round to 6 if the data clearly supports a whole-number multiple.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Calculation\">116 \u00f7 58 = 2<\/td>\n                <td data-label=\"Likely value of n\">2<\/td>\n                <td data-label=\"Exam decision\">Use 2 directly.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n        <div class=\"ols-key-box\">\n          <p><strong>Exam tip:<\/strong> never multiply only one element. The multiplier applies to the whole empirical formula.<\/p>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Molecular Formula Problems<\/h2>\n<p>Work out each molecular formula on paper before you flip the card.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-648\" class=\"h5p-iframe\" data-content-id=\"648\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Molecular Formula Flip Cards: Multi-Step Problems\"><\/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>Empirical Formula vs Molecular Formula<\/h2><\/div>\n        <p>Different compounds may have the same empirical formula but different molecular formulae. This is why relative molecular mass is needed to identify the molecular formula.<\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Empirical formula<\/th>\n                <th>Empirical formula M<sub>r<\/sub><\/th>\n                <th>Compound M<sub>r<\/sub><\/th>\n                <th>n<\/th>\n                <th>Molecular formula<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Empirical formula\">CH<sub>2<\/sub>O<\/td>\n                <td data-label=\"Empirical formula Mr\">30<\/td>\n                <td data-label=\"Compound Mr\">30<\/td>\n                <td data-label=\"n\">1<\/td>\n                <td data-label=\"Molecular formula\">CH<sub>2<\/sub>O<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Empirical formula\">CH<sub>2<\/sub>O<\/td>\n                <td data-label=\"Empirical formula Mr\">30<\/td>\n                <td data-label=\"Compound Mr\">60<\/td>\n                <td data-label=\"n\">2<\/td>\n                <td data-label=\"Molecular formula\">C<sub>2<\/sub>H<sub>4<\/sub>O<sub>2<\/sub><\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Empirical formula\">CH<sub>2<\/sub>O<\/td>\n                <td data-label=\"Empirical formula Mr\">30<\/td>\n                <td data-label=\"Compound Mr\">180<\/td>\n                <td data-label=\"n\">6<\/td>\n                <td data-label=\"Molecular formula\">C<sub>6<\/sub>H<sub>12<\/sub>O<sub>6<\/sub><\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Empirical formula\">HO<\/td>\n                <td data-label=\"Empirical formula Mr\">17<\/td>\n                <td data-label=\"Compound Mr\">34<\/td>\n                <td data-label=\"n\">2<\/td>\n                <td data-label=\"Molecular formula\">H<sub>2<\/sub>O<sub>2<\/sub><\/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: Empirical or Molecular?<\/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-652\" class=\"h5p-iframe\" data-content-id=\"652\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Empirical and Molecular Formulae Summary: Spot the Accurate Statement\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">7<\/div><h2>Common Exam Points<\/h2><\/div>\n        <ul>\n          <li>The molecular formula shows the <strong>number of atoms<\/strong> of each element in one molecule.<\/li>\n          <li>The empirical formula shows the <strong>simplest whole-number ratio<\/strong> of atoms.<\/li>\n          <li>To move from empirical formula to molecular formula, you must be given the compound M<sub>r<\/sub> or enough data to work it out.<\/li>\n          <li>Find the M<sub>r<\/sub> of the empirical formula before calculating the multiplier.<\/li>\n          <li>The multiplier must be a whole number, allowing for sensible rounding of experimental data.<\/li>\n          <li>Apply the multiplier to every atom in the empirical formula, not just the first element.<\/li>\n          <li>If n = 1, the empirical formula and molecular formula are the same.<\/li>\n          <li>Ionic compounds are normally represented by formula units, so the language of molecular formula is mainly used for covalent molecular substances.<\/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>Molecular formula:<\/strong> the number of atoms of each element in one molecule.<\/li>\n          <li><strong>Empirical formula:<\/strong> the simplest whole-number ratio of atoms in a compound.<\/li>\n          <li><strong>Multiplier:<\/strong> n = M<sub>r<\/sub> of compound \u00f7 M<sub>r<\/sub> of empirical formula.<\/li>\n          <li><strong>Method:<\/strong> find the empirical formula M<sub>r<\/sub>, calculate n, then multiply every subscript by n.<\/li>\n          <li><strong>Rounding:<\/strong> experimental M<sub>r<\/sub> data may not be exact, but n should be rounded sensibly to a whole number.<\/li>\n          <li><strong>Shortcut method:<\/strong> percentage composition and M<sub>r<\/sub> can be used together to find the mass of each element in one mole of compound.<\/li>\n          <li><strong>Common error:<\/strong> do not multiply only one element. The whole empirical formula is multiplied.<\/li>\n        <\/ul>\n      <\/section>\n\n      <div class=\"ols-image-lightbox\" id=\"olsImageLightboxMolecularFormula001\" 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-molecular-formula-page\");\n          if (!page) { return; }\n          var lightbox = page.querySelector(\"#olsImageLightboxMolecularFormula001\");\n          if (!lightbox) { return; }\n          var lightboxImage = lightbox.querySelector(\".ols-image-lightbox-img\");\n          var closeButton = 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ease,\r\n        background 0.25s ease,\r\n        color 0.25s ease;\r\n    }\r\n\r\n    .ols-course-cta-aqa-amount-substance .ols-animation-start-overlay:hover .ols-animation-play-circle {\r\n      transform: scale(1.08);\r\n      background: var(--navy);\r\n      color: #ffffff;\r\n    }\r\n\r\n    .ols-course-cta-aqa-amount-substance .ols-animation-play-icon {\r\n      width: 0;\r\n      height: 0;\r\n      margin-left: 7px;\r\n      border-top: 18px solid transparent;\r\n      border-bottom: 18px solid transparent;\r\n      border-left: 28px solid currentColor;\r\n    }\r\n\r\n    .ols-course-cta-aqa-amount-substance .ols-animation-start-text {\r\n      max-width: 540px;\r\n      margin: 0;\r\n      color: #ffffff;\r\n      font-size: clamp(20px, 3vw, 32px);\r\n      line-height: 1.2;\r\n      font-weight: 800;\r\n      text-shadow: 0 8px 20px rgba(0, 0, 0, 0.28);\r\n    }\r\n\r\n    .ols-course-cta-aqa-amount-substance .ols-animation-pause-button {\r\n      position: absolute;\r\n 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{\r\n        width: 100%;\r\n      }\r\n\r\n      .ols-course-cta-aqa-amount-substance .ols-course-cta-stats,\r\n      .ols-course-cta-aqa-amount-substance .ols-course-cta-features {\r\n        grid-template-columns: 1fr;\r\n      }\r\n\r\n      .ols-course-cta-aqa-amount-substance .ols-course-animation-wrap {\r\n        padding: 0;\r\n        border-radius: 0;\r\n      }\r\n\r\n      .ols-course-cta-aqa-amount-substance .ols-animation-frame-shell {\r\n        height: 420px;\r\n        border-radius: 18px;\r\n      }\r\n\r\n      .ols-course-cta-aqa-amount-substance .ols-animation-play-circle {\r\n        width: 76px;\r\n        height: 76px;\r\n      }\r\n\r\n      .ols-course-cta-aqa-amount-substance .ols-animation-play-icon {\r\n        border-top-width: 14px;\r\n        border-bottom-width: 14px;\r\n        border-left-width: 22px;\r\n      }\r\n\r\n      .ols-course-cta-aqa-amount-substance .ols-animation-pause-button {\r\n        left: 12px;\r\n        bottom: 12px;\r\n        min-width: 84px;\r\n        padding: 9px 14px;\r\n        font-size: 13px;\r\n      }\r\n\r\n      .ols-course-cta-aqa-amount-substance .ols-course-button {\r\n        width: 100%;\r\n      }\r\n    }\r\n  <\/style>\r\n\r\n  <div class=\"ols-course-cta-card\">\r\n\r\n    <div class=\"ols-course-cta-top\">\r\n\r\n      <a\r\n        class=\"ols-course-cta-image-link\"\r\n        href=\"[insert here]\"\r\n        aria-label=\"Open the AQA A Level Chemistry 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  --ols-saq-screen-scale:1;\r\n}\r\n\r\nhtml,\r\nbody{\r\n  width:100%;\r\n  height:100%;\r\n}\r\n\r\nbody{\r\n  margin:0;\r\n  overflow:hidden;\r\n  font-family:Poppins,Arial,sans-serif;\r\n  background:#e9efff;\r\n}\r\n\r\n.ols-combined-stage{\r\n  position:relative;\r\n  width:100vw;\r\n  height:100vh;\r\n  overflow:hidden;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n}\r\n\r\n.ols-scene{\r\n  position:absolute;\r\n  inset:0;\r\n  width:100vw;\r\n  height:100vh;\r\n  opacity:0;\r\n  visibility:hidden;\r\n  pointer-events:none;\r\n}\r\n\r\n.ols-scene.active{\r\n  opacity:1;\r\n  visibility:visible;\r\n  pointer-events:auto;\r\n}\r\n\r\n.ols-scene.fade-out{\r\n  animation:olsSceneFadeOut 0.85s ease forwards;\r\n}\r\n\r\n@keyframes olsSceneFadeOut{\r\n  to{\r\n    opacity:0;\r\n    visibility:hidden;\r\n  }\r\n}\r\n\r\n.ols-title-cursor{\r\n  display:inline-block;\r\n  width:5px;\r\n  height:0.85em;\r\n  background:#1C244B;\r\n  margin-left:8px;\r\n  transform:translateY(8px);\r\n  animation:olsBlink 0.8s infinite;\r\n}\r\n\r\n.cursor{\r\n  display:inline-block;\r\n  width:3px;\r\n  height:28px;\r\n  background:#1c244b;\r\n  margin-left:3px;\r\n  transform:translateY(5px);\r\n  animation:olsBlink 0.8s infinite;\r\n}\r\n\r\n@keyframes olsBlink{\r\n  0%,45%{opacity:1;}\r\n  46%,100%{opacity:0;}\r\n}\r\n\r\n.ols-video-stage,\r\n.ols-mcq-stage,\r\n.ols-saq-stage{\r\n  width:100vw;\r\n  height:100vh;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  padding:0;\r\n  overflow:hidden;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n}\r\n\r\n.ols-video-title-screen,\r\n.ols-mcq-intro-screen,\r\n.ols-saq-intro{\r\n  position:absolute;\r\n  inset:0;\r\n  z-index:50;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n  opacity:1;\r\n  visibility:visible;\r\n  pointer-events:none;\r\n}\r\n\r\n.ols-video-title-screen.hide{animation:olsVideoTitleFadeOut 0.85s ease forwards;}\r\n.ols-mcq-intro-screen.hide{animation:olsMcqIntroFadeOut 0.85s ease forwards;}\r\n.ols-saq-intro.hide{animation:olsSaqIntroFadeOut 0.85s ease forwards;}\r\n\r\n@keyframes olsVideoTitleFadeOut{to{opacity:0;visibility:hidden;}}\r\n@keyframes olsMcqIntroFadeOut{to{opacity:0;visibility:hidden;}}\r\n@keyframes olsSaqIntroFadeOut{to{opacity:0;visibility:hidden;}}\r\n\r\n.ols-video-title-wrap,\r\n.ols-mcq-intro-title-wrap,\r\n.ols-saq-intro-title-wrap{\r\n  max-width:1250px;\r\n  padding:0 34px;\r\n  text-align:center;\r\n}\r\n\r\n.ols-video-title,\r\n.ols-mcq-intro-title,\r\n.ols-saq-intro-title{\r\n  margin:0;\r\n  font-family:Poppins,Arial,sans-serif;\r\n  font-size:clamp(52px,8vw,124px);\r\n  font-weight:600;\r\n  line-height:1.08;\r\n  color:#1C244B;\r\n  text-shadow:-9px 0 9px rgba(28,36,75,0.16);\r\n  letter-spacing:-0.045em;\r\n}\r\n\r\n#videoTitleText,\r\n#mcqIntroTitleText,\r\n#saqIntroTitleText{\r\n  white-space:pre-wrap;\r\n}\r\n\r\n.ols-video-scene{\r\n  width:100%;\r\n  height:100%;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  opacity:0;\r\n  visibility:hidden;\r\n}\r\n\r\n.ols-video-scene.show{\r\n  visibility:visible;\r\n  animation:olsVideoSceneIn 1s ease forwards;\r\n}\r\n\r\n@keyframes olsVideoSceneIn{to{opacity:1;}}\r\n\r\n.ols-video-scale-wrap{\r\n  width:calc(var(--ols-video-screen-w) * 1px);\r\n  height:calc(var(--ols-video-screen-h) * 1px);\r\n  transform:scale(var(--ols-video-screen-scale));\r\n  transform-origin:center center;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n}\r\n\r\n.ols-video-card{\r\n  width:1180px;\r\n  height:664px;\r\n  border-radius:28px;\r\n  overflow:hidden;\r\n  background:#1C244B;\r\n  box-shadow:0 28px 80px rgba(28,36,75,0.28);\r\n  transform:translateY(24px) scale(0.96);\r\n  opacity:0;\r\n}\r\n\r\n.ols-video-scene.show .ols-video-card{\r\n  animation:olsVideoCardIn 1s cubic-bezier(.18,.89,.32,1.12) forwards;\r\n  animation-delay:0.2s;\r\n}\r\n\r\n@keyframes olsVideoCardIn{\r\n  to{\r\n    transform:translateY(0) 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<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\" 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The molecular formula shows the number of atoms of each element in one molecule. For example, CH<sub>2<\/sub>O can be an empirical formula, while C<sub>6<\/sub>H<sub>12<\/sub>O<sub>6<\/sub> is the molecular formula of glucose.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>How do I find the molecular formula from the empirical formula?<\/h3>\n            <p>Find the M<sub>r<\/sub> of the empirical formula, divide the compound M<sub>r<\/sub> by this value, then multiply every subscript in the empirical formula by the answer.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>What if the M<sub>r<\/sub> division does not give an exact whole number?<\/h3>\n            <p>Small differences can occur because of rounding in experimental data. If the value is very close to a whole number, round sensibly. A molecular formula must be a whole-number multiple of the empirical formula.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Can the empirical formula and molecular formula be the same?<\/h3>\n            <p>Yes. If the multiplier n is 1, the empirical formula and molecular formula are identical. Water is H<sub>2<\/sub>O as both its empirical and molecular formula.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Can I find the molecular formula directly from percentage composition?<\/h3>\n            <p>Yes, if the compound M<sub>r<\/sub> is also given. Find the mass of each element in one mole of compound using the percentage composition, then divide by the relevant A<sub>r<\/sub> values to find the number of atoms of each element.<\/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 work confidently with formulae and amount-of-substance calculations.<\/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\/empirical-and-molecular-formulae\/empirical-formula\/\">Empirical Formula<\/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\/empirical-and-molecular-formulae\/\">Empirical and Molecular Formulae<\/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\/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\/\">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\/empirical-and-molecular-formulae\/molecular-formula\/#webpage\",\n                        \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/empirical-and-molecular-formulae\/molecular-formula\/\",\n                        \"name\": \"Molecular Formula - AQA A Level Chemistry Revision Notes\",\n                        \"description\": \"AQA A Level Chemistry revision notes explaining molecular formulae, empirical formulae, relative molecular mass, percentage composition and 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        \"acceptedAnswer\": {\n                                                \"@type\": \"Answer\",\n                                                \"text\": \"The empirical formula shows the simplest whole-number ratio of atoms in a compound. The molecular formula shows the number of atoms of each element in one molecule.\"\n                                        }\n                                },\n                                {\n                                        \"@type\": \"Question\",\n                                        \"name\": \"How do I find the molecular formula from the empirical formula?\",\n                                        \"acceptedAnswer\": {\n                                                \"@type\": \"Answer\",\n                                                \"text\": \"Find the relative formula mass of the empirical formula, divide the compound relative molecular mass by this value, then multiply every subscript in the empirical formula by the answer.\"\n                                        }\n                                },\n                                {\n                                        \"@type\": \"Question\",\n                                        \"name\": \"What if the relative molecular mass division does not give an exact whole number?\",\n                                        \"acceptedAnswer\": {\n                                                \"@type\": \"Answer\",\n                                                \"text\": \"Small differences can occur because of rounding in experimental data. If the value is very close to a whole number, round sensibly because a molecular formula must be a whole-number multiple of the empirical formula.\"\n                                        }\n                                },\n                                {\n                                        \"@type\": \"Question\",\n                                        \"name\": \"Can the empirical formula and molecular formula be the same?\",\n                                        \"acceptedAnswer\": {\n                                                \"@type\": \"Answer\",\n                                                \"text\": \"Yes. If the multiplier is 1, the empirical formula and molecular formula are identical.\"\n                                        }\n                                },\n                                {\n                                        \"@type\": \"Question\",\n                                        \"name\": \"Can I find the molecular formula directly from percentage composition?\",\n                                        \"acceptedAnswer\": {\n                                                \"@type\": \"Answer\",\n                                                \"text\": \"Yes, if the compound relative molecular mass is also given. Use the percentage composition to find the mass of each element in one mole of compound, then divide by the relevant relative atomic masses.\"\n                                        }\n                                }\n                        ]\n                }\n        ]\n}\n      <\/script>\n    <\/main>\n  <\/div>\n<\/section>\n","protected":false},"excerpt":{"rendered":"<p>Revision Notes \/ A Level Chemistry \/ AQA \/ 3.1.2 Amount of Substance \/ Empirical and Molecular Formulae \/ Molecular Formula Molecular Formula A focused revision guide to molecular formulae for AQA A Level Chemistry. This page shows how to convert empirical formulae into molecular formulae using relative molecular mass, percentage composition and worked examples. 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