{"id":66480,"date":"2026-10-06T17:20:34","date_gmt":"2026-10-06T14:20:34","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66480"},"modified":"2026-10-06T17:20:34","modified_gmt":"2026-10-06T14:20:34","slug":"clausius-clapeyron-calculator","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/chemistry\/clausius-clapeyron-calculator\/","title":{"rendered":"Clausius\u2013Clapeyron 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\">Estimate Vapor Pressure at a New Temperature<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66480\" data-favorite-title=\"Clausius\u2013Clapeyron\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/chemistry\/clausius-clapeyron-calculator\/\" data-favorite-excerpt=\"Estimate the vapor pressure of a liquid at any temperature from one known pressure\u2013temperature pair and the enthalpy of vaporization, using the integrated Clausius\u2013Clapeyron equation. Enter the known conditions, the target temperature, and \u0394Hvap.\" 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\/clausius-clapeyron-calculator\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66480\" data-post=\"66480\"><fieldset class=\"fieldset-input is-1\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Known Vapor Pressure (P\u2081)<\/label><div class=\"term\">P\u2081<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"text\" name=\"known_vapor_pressure_p\" id=\"field-1\" aria-describedby=\"calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 760\" min=\"0\" value=\"760\"\/><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"unit\" aria-label=\"Unit\"><option value=\"mmhg\" selected>mmHg<\/option><option value=\"kpa\">kPa<\/option><option value=\"atm\">atm<\/option><option value=\"pa\">Pa<\/option><option value=\"bar\">bar<\/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><small id=\"calc-info-1\">Vapor pressure of the liquid at the known temperature<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-3\">Known Temperature (T\u2081)<\/label><div class=\"term\">T\u2081<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"number\" name=\"known_temperature_t\" id=\"field-3\" aria-describedby=\"calc-info-3\" placeholder=\"e.g. 100\" step=\"0.01\" value=\"100\"\/><div class=\"grid grid-cols-1\"><select id=\"field-4\" name=\"unit\" aria-label=\"Unit\"><option value=\"c\" selected>\u00b0C<\/option><option value=\"k\">K<\/option><option value=\"f\">\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><small id=\"calc-info-3\">Temperature at which the known vapor pressure was measured<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-5\">Target Temperature (T\u2082)<\/label><div class=\"term\">T\u2082<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"number\" name=\"target_temperature_t\" id=\"field-5\" aria-describedby=\"calc-info-5\" placeholder=\"e.g. 25\" step=\"0.01\" value=\"25\"\/><div class=\"grid grid-cols-1\"><select id=\"field-6\" name=\"unit\" aria-label=\"Unit\"><option value=\"c\" selected>\u00b0C<\/option><option value=\"k\">K<\/option><option value=\"f\">\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><small id=\"calc-info-5\">Temperature at which you want to estimate the vapor pressure<\/small><\/div><div class=\"field has-term\" id=\"input-4\"><label for=\"field-7\">Enthalpy of Vaporization (\u0394Hvap)<\/label><div class=\"term\">\u0394Hvap<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"text\" name=\"enthalpy_of_vaporization_hvap\" id=\"field-7\" aria-describedby=\"calc-info-7\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 40.7\" min=\"0.0001\" value=\"40.7\"\/><div class=\"grid grid-cols-1\"><select id=\"field-8\" name=\"unit\" aria-label=\"Unit\"><option value=\"kj_mol\" selected>kJ\/mol<\/option><option value=\"j_mol\">J\/mol<\/option><option value=\"kcal_mol\">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><small id=\"calc-info-7\">Heat required to vaporize one mole of the liquid (40.7 kJ\/mol for water near its boiling point)<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66480\">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> Vapor Pressure Results<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Vapor Pressure at T\u2082 (in your P\u2081 unit)<\/span><span class=\"result-term\">P\u2082<\/span><\/span><span class=\"field-value\" id=\"result-1\"><\/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>Vapor Pressure at T\u2082<\/span><\/span><span class=\"field-value\" id=\"result-2\" data-unit=\"kPa\"><\/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-3\"><span class=\"field-title\"><span>Vapor Pressure at T\u2082<\/span><\/span><span class=\"field-value\" id=\"result-3\" data-unit=\"atm\"><\/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-4\"><span class=\"field-title\"><span>Vapor Pressure at T\u2082<\/span><\/span><span class=\"field-value\" id=\"result-4\" data-unit=\"mmHg\"><\/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=\"66480\" 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>Clausius\u2013Clapeyron 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\\[ \\ln\\!\\left(\\frac{P_2}{P_1}\\right) = -\\frac{\\Delta H_{vap}}{R}\\left(\\frac{1}{T_2} - \\frac{1}{T_1}\\right) \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(P_1\\) \u2014 vapor pressure at the known temperature (any pressure unit)<\/li>\n<li>\\(P_2\\) \u2014 vapor pressure at the target temperature (same unit as \\(P_1\\))<\/li>\n<li>\\(T_1\\) \u2014 known temperature (kelvin)<\/li>\n<li>\\(T_2\\) \u2014 target temperature (kelvin)<\/li>\n<li>\\(\\Delta H_{vap}\\) \u2014 enthalpy of vaporization (J\/mol)<\/li>\n<li>\\(R\\) \u2014 gas constant, \\(8.314\\ \\text{J\/(mol\u00b7K)}\\)<\/li>\n<\/ul>\n<p>This is the integrated form of the Clausius\u2013Clapeyron equation. It assumes the vapor behaves as an ideal gas and that the enthalpy of vaporization is constant over the temperature range, and it predicts how vapor pressure changes exponentially with temperature.<\/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>Clausius\u2013Clapeyron \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> water boils at 100 \u00b0C at 760 mmHg (1 atm). Estimate the vapor pressure of water at 25 \u00b0C, using \\(\\Delta H_{vap} = 40.7\\ \\text{kJ\/mol}\\).<\/p>\n<p>Convert temperatures to kelvin: \\(T_1 = 373.15\\ \\text{K}\\), \\(T_2 = 298.15\\ \\text{K}\\), and \\(\\Delta H_{vap} = 40\\,700\\ \\text{J\/mol}\\).<\/p>\n<p>\\[ \\ln\\!\\left(\\frac{P_2}{760}\\right) = -\\frac{40\\,700}{8.314}\\left(\\frac{1}{298.15} - \\frac{1}{373.15}\\right) = -4894.9 \\times 0.000674 = -3.300 \\]<\/p>\n<p>\\[ P_2 = 760 \\times e^{-3.300} \\]<\/p>\n<p><strong>Result:<\/strong> \\(P_2 \\approx 28.04\\ \\text{mmHg}\\), which is about 3.74 kPa or 0.0369 atm. (The measured value is 23.76 mmHg \u2014 the difference comes from \u0394Hvap not being perfectly constant; see the notes below.)<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Enter the <strong>Known Vapor Pressure (P\u2081)<\/strong> of the liquid and select its unit (mmHg, kPa, atm, Pa, or bar). A boiling point at a known pressure works well here.<\/li>\n<li>Enter the <strong>Known Temperature (T\u2081)<\/strong> at which that pressure was measured, in \u00b0C, K, or \u00b0F.<\/li>\n<li>Enter the <strong>Target Temperature (T\u2082)<\/strong> at which you want to estimate the vapor pressure, in any of the same temperature units.<\/li>\n<li>Enter the <strong>Enthalpy of Vaporization (\u0394Hvap)<\/strong> and choose kJ\/mol, J\/mol, or kcal\/mol. Reference tables for common liquids list this value.<\/li>\n<li>Read the results: the estimated vapor pressure at T\u2082 is shown in your chosen pressure unit, plus conversions to kPa, atm, and mmHg.<\/li>\n<\/ol>\n<h2>What Is the Clausius\u2013Clapeyron Equation?<\/h2>\n<p>The Clausius\u2013Clapeyron equation describes the relationship between the vapor pressure of a liquid and temperature. Vapor pressure rises steeply with temperature because more molecules have enough energy to escape the liquid phase. The equation quantifies this: a plot of \\(\\ln P\\) against \\(1\/T\\) is a straight line with slope \\(-\\Delta H_{vap}\/R\\). Liquids with a high enthalpy of vaporization, such as water, show a steeper temperature dependence than volatile liquids like acetone or ether.<\/p>\n<p>The integrated form used by this calculator needs only one reference point \u2014 typically a boiling point \u2014 to estimate vapor pressure at any other temperature. This is the standard back-of-the-envelope method in chemistry and chemical engineering for interpolation, since direct measurements are not always available at the temperature of interest.<\/p>\n<p>Interpreting the result is straightforward: if \\(T_2  T_1\\), it rises. For example, the calculation above shows why water evaporates at room temperature even though it boils at 100 \u00b0C \u2014 its vapor pressure at 25 \u00b0C is still about 0.037 atm. Vapor pressure also determines boiling behavior: a liquid boils when its vapor pressure equals the surrounding pressure, which is why water boils below 100 \u00b0C at altitude.<\/p>\n<p>If you work with gas-phase problems generally, you may also find our <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/combined-gas-law\/\">Combined Gas Law calculator<\/a> and <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/daltons-law\/\">Dalton's Law calculator<\/a> useful. The same exponential temperature dependence appears in kinetics \u2014 see the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/arrhenius-equation-2\/\">Arrhenius Equation calculator<\/a>.<\/p>\n<h2>Assumptions, Limitations, and Practical Tips<\/h2>\n<ul>\n<li><strong>Constant \u0394Hvap.<\/strong> The enthalpy of vaporization actually decreases with temperature and reaches zero at the critical point. Over ranges of 20\u201350 K the error is usually small, but over hundreds of kelvin it grows \u2014 the water example above overestimates by about 18% because \u0394Hvap falls from 40.7 kJ\/mol at 100 \u00b0C to about 44 kJ\/mol near 25 \u00b0C in reality. Use a \u0394Hvap value measured near the midpoint of your temperature range for better accuracy.<\/li>\n<li><strong>Ideal gas vapor.<\/strong> The derivation neglects the molar volume of the liquid and assumes the vapor obeys the ideal gas law. This is an excellent approximation at low pressures (below a few atmospheres).<\/li>\n<li><strong>Only for vapor\u2013liquid equilibrium.<\/strong> The equation applies to a pure substance. It does not describe solutions, where Raoult's law or activity coefficients are needed, and it should not be extrapolated above the critical temperature.<\/li>\n<li><strong>Choose a reliable reference point.<\/strong> A normal boiling point (1 atm) from a handbook is a good anchor; so is any tabulated vapor pressure value.<\/li>\n<li><strong>Watch the units.<\/strong> Temperature must be in kelvin in the formula itself; the calculator converts \u00b0C and \u00b0F for you. Keep \u0394Hvap and R consistent \u2014 the calculator handles the conversion to J\/mol internally.<\/li>\n<\/ul>\n<p>For quick reference, enthalpies of vaporization at the normal boiling point include water (40.7 kJ\/mol), ethanol (38.6 kJ\/mol), methanol (35.2 kJ\/mol), acetone (29.1 kJ\/mol), and benzene (30.8 kJ\/mol).<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Estimate the vapor pressure of a liquid at any temperature from one known pressure\u2013temperature pair and the enthalpy of vaporization, using the integrated Clausius\u2013Clapeyron equation. Enter the known conditions, the target temperature, and \u0394Hvap.<\/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-66480","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\/66480","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=66480"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66480\/revisions"}],"predecessor-version":[{"id":66481,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66480\/revisions\/66481"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66480"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66480"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66480"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}