{"id":66539,"date":"2026-10-07T08:30:16","date_gmt":"2026-10-07T05:30:16","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66539"},"modified":"2026-10-07T08:30:16","modified_gmt":"2026-10-07T05:30:16","slug":"hesss-law-calculator","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/chemistry\/hesss-law-calculator\/","title":{"rendered":"Hess's Law Calculator"},"content":{"rendered":"<section class=\"not-prose calculator-box\" aria-labelledby=\"calculator-title\"><div class=\"flex items-baseline sm:items-center justify-between gap-2 sm:gap-3\"><div class=\"flex flex-col sm:flex-row sm:items-center gap-2\"><span class=\"icon icon-calculator text-primary-700! text-base! dark:text-primary-300!\" aria-hidden=\"true\"><\/span><h2 id=\"calculator-title\" class=\"text-lg font-display font-bold\">Find a Reaction&#039;s Enthalpy from Other Reactions or from Formation Enthalpies<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66539\" data-favorite-title=\"Hess&#039;s Law\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/chemistry\/hesss-law-calculator\/\" data-favorite-excerpt=\"Calculate the enthalpy change of any reaction using Hess&#039;s law: combine known reactions with multipliers, or build the target reaction from standard formation enthalpies. Enter your values and get the result in kJ\/mol and kcal\/mol.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-chemistry-1\">\n    <span class=\"icon icon-shape-star-empty\" aria-hidden=\"true\"><\/span>\n  <\/button>\n  <div class=\"calcdash-favorite__tip\" aria-hidden=\"true\">\n   <span class=\"favorite-tooltip\" id=\"favorite-tooltip\"><\/span>\n  <\/div>\n  <span class=\"sr-only\" role=\"status\" id=\"favorite-status\"><\/span>\n<\/div><\/div><form action=\"https:\/\/wpcalc.com\/en\/chemistry\/hesss-law-calculator\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66539\" data-post=\"66539\"><fieldset class=\"fieldset-input is-2\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field is-single\" id=\"input-1\"><label for=\"field-1\">Calculation Method<\/label><div class=\"grid grid-cols-1\"><select id=\"field-1\" name=\"calculation_method\"><option value=\"reactions\" selected>Add known reactions (Hess cycle)<\/option><option value=\"formation\">From standard formation enthalpies (\u0394H\u00b0f)<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><div class=\"field is-single\" id=\"input-2\"><label for=\"field-2\">Energy Unit of Entered Values<\/label><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"energy_unit_of_entered_values\"><option value=\"kJ\" selected>kJ\/mol<\/option><option value=\"kcal\">kcal\/mol<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><div class=\"is-single field\" id=\"input-3\"><span class=\"font-semibold\">Known Reactions (Hess Cycle)<\/span><\/div><div class=\"field is-single\" id=\"input-4\"><label for=\"field-4\">\u0394H of Each Known Reaction<\/label><textarea id=\"field-4\" name=\"h_of_each_known_reaction\">-393.5; -283.0<\/textarea><\/div><div class=\"field is-single\" id=\"input-5\"><label for=\"field-5\">Multiplier of Each Reaction<\/label><textarea id=\"field-5\" name=\"multiplier_of_each_reaction\">1; -1<\/textarea><\/div><div class=\"is-single field\" id=\"input-6\" hidden><span class=\"font-semibold\">Standard Formation Enthalpies<\/span><\/div><div class=\"field is-single\" id=\"input-7\" hidden><label for=\"field-7\">\u0394H\u00b0f of Each Product<\/label><textarea id=\"field-7\" name=\"hf_of_each_product\">-393.5; -285.8<\/textarea><\/div><div class=\"field is-single\" id=\"input-8\" hidden><label for=\"field-8\">Coefficient of Each Product<\/label><textarea id=\"field-8\" name=\"coefficient_of_each_product\">1; 2<\/textarea><\/div><div class=\"field is-single\" id=\"input-9\" hidden><label for=\"field-9\">\u0394H\u00b0f of Each Reactant<\/label><textarea id=\"field-9\" name=\"hf_of_each_reactant\">-74.8; 0<\/textarea><\/div><div class=\"field is-single\" id=\"input-10\" hidden><label for=\"field-10\">Coefficient of Each Reactant<\/label><textarea id=\"field-10\" name=\"coefficient_of_each_reactant\">1; 2<\/textarea><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66539\">Calculate<\/button><button type=\"reset\">Reset<\/button><\/div><div class=\"field is-checkbox hidden!\" id=\"field-auto-calc\"><input type=\"checkbox\" id=\"auto-calc\"><label for=\"auto-calc\">Calculate automatically<\/label><small>If enabled, the result will update automatically when you change any value.<\/small><\/div><div class=\"fieldset-result is-hidden\" aria-labelledby=\"result-title\" aria-live=\"polite\" role=\"region\"> <h3 class=\"result-title bg-gradient-to-r from-primary-50 to-gray-50 dark:from-primary-900 dark:to-gray-800\" id=\"result-title\"><span class=\"icon icon-s-pulse\" aria-hidden=\"true\"><\/span> Hess&#039;s Law Results<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Reaction Enthalpy<\/span><span class=\"result-term\">\u0394H\u00b0rxn<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"kJ\/mol\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-2\"><span class=\"field-title\"><span>Equivalent in kcal\/mol<\/span><\/span><span class=\"field-value\" id=\"result-2\" data-unit=\"kcal\/mol\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result is-column\" id=\"output-3\"><span class=\"field-title\"><span>Interpretation<\/span><\/span><span class=\"field-value\" id=\"result-3\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result is-column\" id=\"output-4\"><span class=\"field-title\"><span>Calculation Details<\/span><\/span><span class=\"field-value\" id=\"result-4\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><\/div><div class=\"result-actions\"><button type=\"button\" class=\"copy-link\"><svg viewBox=\"0 0 20 20\" fill=\"currentColor\" aria-hidden=\"true\"><path d=\"M12.232 4.232a2.5 2.5 0 0 1 3.536 3.536l-1.225 1.224a.75.75 0 0 0 1.061 1.06l1.224-1.224a4 4 0 0 0-5.656-5.656l-3 3a4 4 0 0 0 .225 5.865.75.75 0 0 0 .977-1.138 2.5 2.5 0 0 1-.142-3.667l3-3Z\"\/><path d=\"M11.603 7.963a.75.75 0 0 0-.977 1.138 2.5 2.5 0 0 1 .142 3.667l-3 3a2.5 2.5 0 0 1-3.536-3.536l1.225-1.224a.75.75 0 0 0-1.061-1.06l-1.224 1.224a4 4 0 1 0 5.656 5.656l3-3a4 4 0 0 0-.225-5.865Z\"\/><\/svg><span class=\"copy-link__text\">Copy link to this calculation<\/span><\/button><span class=\"sr-only\" role=\"status\" id=\"copy-link-status\"><\/span><\/div><\/div><a href=\"#respond\" class=\"hidden transition-opacity duration-300 opacity-0 w-50 text-sm justify-center items-center gap-2 px-4 py-2 rounded bg-gray-200 text-gray-700 hover:bg-gray-300\" id=\"leave-comment\"><span class=\"icon icon-comments\" aria-hidden=\"true\"><\/span>Leave a Comment<\/a><\/form><\/section><section id=\"calc-reactions\" class=\"not-prose hidden my-12 bg-gradient-to-r from-primary-50 to-gray-50 border border-indigo-100 rounded-xl px-6 py-4 shadow-sm\" data-post=\"66539\" aria-live=\"polite\" aria-labelledby=\"calc-reactions-title\"><p id=\"calc-reactions-title\" class=\"text-sm text-gray-500 text-center mb-2\">How did this result make you feel?<\/p><div role=\"group\" aria-labelledby=\"calc-reactions-title\" class=\"grid grid-cols-3 sm:flex sm:flex-row sm:justify-around gap-4 sm:items-center sm:flex-wrap\"><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"like\"><span class=\"reaction-count\" data-reaction-count=\"like\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude00 <\/span><span class=\"reaction-description font-medium\">Like <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"helpful\"><span class=\"reaction-count\" data-reaction-count=\"helpful\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\udca1 <\/span><span class=\"reaction-description font-medium\">Helpful <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"confused\"><span class=\"reaction-count\" data-reaction-count=\"confused\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude15 <\/span><span class=\"reaction-description font-medium\">Confused <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"disappointed\"><span class=\"reaction-count\" data-reaction-count=\"disappointed\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude1e <\/span><span class=\"reaction-description font-medium\">Disappointed <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"inaccurate\"><span class=\"reaction-count\" data-reaction-count=\"inaccurate\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\u274c <\/span><span class=\"reaction-description font-medium\">Inaccurate <\/span><\/button><\/div><div id=\"reaction-message\" class=\"hidden mt-8 rounded-md border border-primary-100 bg-white\/50 backdrop-blur-sm px-4 py-2 text-sm text-center shadow-sm\"><\/div><\/section><div class=\"calcdash-ad not-prose calcdash-ad--calc_result calcdash-ad--in-article\"><ins class=\"adsbygoogle\" style=\"display:block\" data-ad-client=\"ca-pub-1721569815777345\" data-ad-slot=\"6317458308\" data-ad-layout=\"in-article\" data-ad-format=\"fluid\"><\/ins><script>(adsbygoogle = window.adsbygoogle || []).push({});<\/script><\/div>\n<style id=\"wpcoderpro-inline-1\">.formula-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section class=\"formula-box\" aria-labelledby=\"formula-title\">\r\n\t<div id=\"formula-title\" class=\"not-prose font-display mb-4\"><span class=\"icon icon-formula\" aria-hidden=\"true\"><\/span><h2>Hess's Law Formula<\/h2><\/div>\r\n\t<figure class=\"not-prose formula\">\r\n\t\t<figcaption class=\"formula-title\">Formula<\/figcaption>\r\n\t\t<div class=\"text-base text-gray-800\" id=\"formula\">\n\\[ \\Delta H^\\circ_{\\mathrm{rxn}} = \\sum_i n_i \\, \\Delta H^\\circ_i \\\\[4pt] \\Delta H^\\circ_{\\mathrm{rxn}} = \\sum_{\\text{products}} \\nu \\, \\Delta H^\\circ_f \\; - \\sum_{\\text{reactants}} \\nu \\, \\Delta H^\\circ_f \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(\\Delta H^\\circ_{\\mathrm{rxn}}\\) \u2014 standard enthalpy change of the target reaction (kJ\/mol)<\/li>\n<li>\\(n_i\\) \u2014 multiplier applied to known reaction \\(i\\) (\u22121 reverses it, \u00bd takes half of it)<\/li>\n<li>\\(\\Delta H^\\circ_i\\) \u2014 enthalpy change of known reaction \\(i\\) (kJ\/mol)<\/li>\n<li>\\(\\nu\\) \u2014 stoichiometric coefficient of a substance in the balanced equation<\/li>\n<li>\\(\\Delta H^\\circ_f\\) \u2014 standard formation enthalpy of a substance (kJ\/mol)<\/li>\n<\/ul>\n<p>Enthalpy is a state function: it depends only on the initial and final states, not on the path taken. Both formulas express the same idea \u2014 the enthalpy change of a reaction is the same whether it happens in one step or in any number of steps.<\/p>\n<p>\r\n<\/section>\n<style id=\"wpcoderpro-inline-459\">.calculation-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section id=\"calculation\" class=\"calculation-box\" aria-labelledby=\"calculation-title\">\r\n\t<div id=\"calculation-title\" class=\"not-prose font-display\"><span class=\"icon icon-unordered-list\" aria-hidden=\"true\"><\/span><h2>Hess's Law \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> find the enthalpy of formation of carbon monoxide, \\( \\mathrm{C(graphite) + \\tfrac{1}{2}O_2(g) \\to CO(g)} \\), from two measured reactions: the combustion of graphite \\( \\mathrm{C + O_2 \\to CO_2} \\) with \\(\\Delta H^\\circ_1 = -393.5\\) kJ\/mol, and the combustion of carbon monoxide \\( \\mathrm{CO + \\tfrac{1}{2}O_2 \\to CO_2} \\) with \\(\\Delta H^\\circ_2 = -283.0\\) kJ\/mol.<\/p>\n<p>The second reaction must be reversed so that CO appears as a product, so its multiplier is \u22121:<\/p>\n<p>\\[ \\Delta H^\\circ_{\\mathrm{rxn}} = (1)\\times(-393.5) + (-1)\\times(-283.0) = -393.5 + 283.0 \\]<\/p>\n<p><strong>Result:<\/strong> \\(\\Delta H^\\circ_{\\mathrm{rxn}} = -110.5\\) kJ\/mol, which equals \u221226.41 kcal\/mol. These are exactly the calculator's default values, so you can reproduce the result immediately.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Hess's Law Calculator<\/h2>\n<ol>\n<li>Choose a <strong>Calculation Method<\/strong>: \"Add known reactions (Hess cycle)\" to combine measured reactions, or \"From standard formation enthalpies (\u0394H\u00b0f)\" to build the reaction from tabulated values.<\/li>\n<li>Set the <strong>Energy Unit of Entered Values<\/strong> to kJ\/mol or kcal\/mol. The result is shown in both units regardless of your choice.<\/li>\n<li>For the Hess-cycle method, enter the <strong>\u0394H of Each Known Reaction<\/strong>, separated by semicolons, spaces or new lines (e.g. <code>-393.5; -283.0<\/code>).<\/li>\n<li>Enter the <strong>Multiplier of Each Reaction<\/strong> in the same order. Use \u22121 to reverse a reaction, \u00bd for half of it, or leave the field empty to use 1 for every reaction.<\/li>\n<li>For the formation-enthalpy method, list the <strong>\u0394H\u00b0f of Each Product<\/strong> and <strong>\u0394H\u00b0f of Each Reactant<\/strong>, then give the matching stoichiometric <strong>coefficients<\/strong>. Use 0 for elements in their standard state, such as O\u2082(g) or C(graphite).<\/li>\n<li>Read the <strong>Reaction Enthalpy<\/strong>, its equivalent in kcal\/mol, an interpretation (exothermic or endothermic) and a step-by-step calculation in the results panel.<\/li>\n<\/ol>\n<h2>What Is Hess's Law?<\/h2>\n<p>Hess's law states that the total enthalpy change of a chemical reaction is the same regardless of the route by which the reaction occurs. If a target reaction can be written as the sum (or difference) of other reactions, its enthalpy change is the corresponding sum of the individual enthalpy changes. This works because enthalpy is a <em>state function<\/em>: only the starting and ending states matter, not the path between them.<\/p>\n<p>This principle is enormously practical. Some reactions are impossible to measure directly \u2014 carbon cannot be burned to pure CO without also producing some CO\u2082, so the formation enthalpy of CO must be obtained indirectly, exactly as in the example above. With Hess's law, any hard-to-measure reaction can be assembled from reactions that are easy to run in a calorimeter.<\/p>\n<p>The second calculation method is a special case of the same idea. Every substance is assigned a standard formation enthalpy \\(\\Delta H^\\circ_f\\), the enthalpy change when one mole of it forms from its elements in their standard states. Since formation is a common \"path\" to both reactants and products, the reaction enthalpy is simply the sum of the products' formation enthalpies minus the sum of the reactants'. By definition, \\(\\Delta H^\\circ_f = 0\\) for any element already in its standard state.<\/p>\n<p>To interpret the sign: a negative \\(\\Delta H^\\circ_{\\mathrm{rxn}}\\) means the reaction is <strong>exothermic<\/strong> (heat is released, products lie lower in enthalpy than reactants), while a positive value means it is <strong>endothermic<\/strong> (heat is absorbed). The magnitude is the heat exchanged per mole of reaction <em>as written<\/em>, so doubling all coefficients doubles the enthalpy change.<\/p>\n<h2>Assumptions, Limitations and Tips<\/h2>\n<ul>\n<li><strong>Standard conditions:<\/strong> the calculator assumes all values refer to the same standard state (usually 298 K, 1 bar) and the same physical states of the substances. Mixing values for different states (e.g. H\u2082O(g) vs H\u2082O(l)) gives wrong results \u2014 check the state labels in your data table.<\/li>\n<li><strong>Multipliers scale the reaction:<\/strong> when you multiply a reaction by \\(n\\), its enthalpy change is also multiplied by \\(n\\), and when you reverse a reaction the sign of \\(\\Delta H\\) flips. The calculator applies this automatically.<\/li>\n<li><strong>Per mole of reaction:<\/strong> the result refers to the reaction exactly as you balanced it. Always confirm the stoichiometric coefficients before comparing with literature values.<\/li>\n<li><strong>Hess cycles must cancel cleanly:<\/strong> intermediate species must appear on both sides and cancel out. The calculator checks the arithmetic; verifying that the cycle is chemically valid is up to you.<\/li>\n<li><strong>Unit conversion:<\/strong> the calculator converts at 1 kcal = 4.184 kJ (exact) and reports the answer in both units.<\/li>\n<\/ul>\n<h2>Common Standard Formation Enthalpies (kJ\/mol, 298 K)<\/h2>\n<table>\n<thead>\n<tr>\n<th>Substance<\/th>\n<th>\\(\\Delta H^\\circ_f\\) (kJ\/mol)<\/th>\n<th>Substance<\/th>\n<th>\\(\\Delta H^\\circ_f\\) (kJ\/mol)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>CO\u2082(g)<\/td>\n<td>\u2212393.5<\/td>\n<td>CH\u2084(g)<\/td>\n<td>\u221274.8<\/td>\n<\/tr>\n<tr>\n<td>H\u2082O(l)<\/td>\n<td>\u2212285.8<\/td>\n<td>C\u2082H\u2086(g)<\/td>\n<td>\u221284.7<\/td>\n<\/tr>\n<tr>\n<td>H\u2082O(g)<\/td>\n<td>\u2212241.8<\/td>\n<td>C\u2083H\u2088(g)<\/td>\n<td>\u2212103.8<\/td>\n<\/tr>\n<tr>\n<td>CO(g)<\/td>\n<td>\u2212110.5<\/td>\n<td>NH\u2083(g)<\/td>\n<td>\u221246.1<\/td>\n<\/tr>\n<tr>\n<td>NO(g)<\/td>\n<td>+90.3<\/td>\n<td>SO\u2082(g)<\/td>\n<td>\u2212296.8<\/td>\n<\/tr>\n<tr>\n<td>HCl(g)<\/td>\n<td>\u221292.3<\/td>\n<td>Elements in standard state<\/td>\n<td>0 (by definition)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Values may vary slightly between reference tables; use one consistent source for all entries. To measure enthalpy changes experimentally, see the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/calorimetry-calculator\/\">Calorimetry Calculator<\/a>. Once you know \\(\\Delta H^\\circ\\), you can connect it to equilibrium behaviour with the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/equilibrium-constant-calculator\/\">Equilibrium Constant Calculator<\/a> or study its temperature dependence with the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/van-t-hoff-equation-calculator\/\">Van 't Hoff Equation Calculator<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calculate the enthalpy change of any reaction using Hess's law: combine known reactions with multipliers, or build the target reaction from standard formation enthalpies. Enter your values and get the result in kJ\/mol and kcal\/mol.<\/p>\n","protected":false},"author":3168,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[54],"tags":[57],"class_list":["post-66539","post","type-post","status-publish","format-standard","hentry","category-chemistry","tag-reactions"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66539","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/users\/3168"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/comments?post=66539"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66539\/revisions"}],"predecessor-version":[{"id":66540,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66539\/revisions\/66540"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66539"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66539"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66539"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}