{"id":2130,"date":"2026-10-14T22:06:19","date_gmt":"2026-10-14T21:06:19","guid":{"rendered":"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-lei-de-kirchhoff-termoquimica\/"},"modified":"2026-10-14T22:06:19","modified_gmt":"2026-10-14T21:06:19","slug":"calculadora-lei-de-kirchhoff-termoquimica","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-lei-de-kirchhoff-termoquimica\/","title":{"rendered":"Calculadora da Lei de Kirchhoff da Termoqu\u00edmica"},"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\">Ajuste a entalpia de rea\u00e7\u00e3o de uma temperatura para outra<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"2130\" data-favorite-title=\"Lei de Kirchhoff da Termoqu\u00edmica\" data-favorite-url=\"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-lei-de-kirchhoff-termoquimica\/\" data-favorite-excerpt=\"Converta a entalpia de uma rea\u00e7\u00e3o de uma temperatura para outra usando a lei de Kirchhoff. Informe a entalpia conhecida na temperatura de refer\u00eancia, a temperatura desejada e as somas das capacidades t\u00e9rmicas de reagentes e produtos.\" aria-label=\"Adicionar aos favoritos\" 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\/pt\/quimica\/calculadora-lei-de-kirchhoff-termoquimica\/\" method=\"POST\" class=\"calculator\" id=\"calculator-2130\" data-post=\"2130\"><fieldset class=\"fieldset-input is-2\"><legend class=\"sr-only\">Campos de entrada<\/legend><div class=\"is-single field\" id=\"input-1\"><span class=\"font-semibold\">Entalpia na temperatura de refer\u00eancia<\/span><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">Entalpia de rea\u00e7\u00e3o na temperatura de refer\u00eancia (\u0394H\u2081)<\/label><div class=\"term\">\u0394H\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=\"entalpia_de_reao_na_temperatura_de_referncia_h\" id=\"field-2\" aria-describedby=\"calc-info-2\" placeholder=\"e.g. -92.2\" step=\"any\" value=\"-92.2\"\/><div class=\"grid grid-cols-1\"><select id=\"field-3\" name=\"unidade\" aria-label=\"Unidade\"><option value=\"kJ_mol\" selected>kJ\/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-2\">Entalpia-padr\u00e3o de rea\u00e7\u00e3o (por exemplo, \u0394H\u00b0f a 298,15 K). Negativa para rea\u00e7\u00f5es exot\u00e9rmicas, positiva para endot\u00e9rmicas.<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-4\">Temperatura de refer\u00eancia (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=\"text\" name=\"temperatura_de_referncia_t\" id=\"field-4\" aria-describedby=\"calc-info-4\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 298.15\" min=\"0\" value=\"298.15\"\/><div class=\"grid grid-cols-1\"><select id=\"field-5\" name=\"unidade\" aria-label=\"Unidade\"><option value=\"K\" selected>K<\/option><option value=\"C\">\u00b0C<\/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-4\">Temperatura na qual \u0394H\u2081 \u00e9 conhecido \u2014 normalmente a temperatura-padr\u00e3o de refer\u00eancia de 298,15 K (25 \u00b0C).<\/small><\/div><div class=\"is-single field\" id=\"input-4\"><span class=\"font-semibold\">Temperatura-alvo<\/span><\/div><div class=\"field has-term\" id=\"input-5\"><label for=\"field-7\">Temperatura-alvo (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=\"text\" name=\"temperaturaalvo_t\" id=\"field-7\" aria-describedby=\"calc-info-7\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 400\" min=\"0\" value=\"400\"\/><div class=\"grid grid-cols-1\"><select id=\"field-8\" name=\"unidade\" aria-label=\"Unidade\"><option value=\"K\" selected>K<\/option><option value=\"C\">\u00b0C<\/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-7\">Temperatura na qual a entalpia de rea\u00e7\u00e3o deve ser estimada.<\/small><\/div><div class=\"is-single field\" id=\"input-6\"><span class=\"font-semibold\">Capacidades t\u00e9rmicas molares (soma de todas as esp\u00e9cies, Cp \u00d7 coeficiente estequiom\u00e9trico)<\/span><\/div><div class=\"field has-term\" id=\"input-7\"><label for=\"field-10\">Soma das capacidades t\u00e9rmicas dos reagentes (\u03a3Cp, reagentes)<\/label><div class=\"term\">\u03a3Cp,r<\/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=\"soma_das_capacidades_trmicas_dos_reagentes_cp_reagentes\" id=\"field-10\" aria-describedby=\"calc-info-10\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 115.5\" min=\"0\" value=\"115.5\"\/><div class=\"grid grid-cols-1\"><select id=\"field-11\" name=\"unidade\" aria-label=\"Unidade\"><option value=\"J_molK\" selected>J\/(mol\u00b7K)<\/option><option value=\"kJ_molK\">kJ\/(mol\u00b7K)<\/option><option value=\"cal_molK\">cal\/(mol\u00b7K)<\/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-10\">\u03a3 Cp \u00d7 \u03bd sobre todos os reagentes. Exemplo N\u2082 + 3H\u2082: 29,1 + 3 \u00d7 28,8 = 115,5 J\/(mol\u00b7K).<\/small><\/div><div class=\"field has-term\" id=\"input-8\"><label for=\"field-12\">Soma das capacidades t\u00e9rmicas dos produtos (\u03a3Cp, produtos)<\/label><div class=\"term\">\u03a3Cp,p<\/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=\"soma_das_capacidades_trmicas_dos_produtos_cp_produtos\" id=\"field-12\" aria-describedby=\"calc-info-12\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 71.2\" min=\"0\" value=\"71.2\"\/><div class=\"grid grid-cols-1\"><select id=\"field-13\" name=\"unidade\" aria-label=\"Unidade\"><option value=\"J_molK\" selected>J\/(mol\u00b7K)<\/option><option value=\"kJ_molK\">kJ\/(mol\u00b7K)<\/option><option value=\"cal_molK\">cal\/(mol\u00b7K)<\/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-12\">\u03a3 Cp \u00d7 \u03bd sobre todos os produtos. Exemplo 2NH\u2083: 2 \u00d7 35,6 = 71,2 J\/(mol\u00b7K).<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Recalcular\" id=\"calculate-button\" data-post=\"2130\">Calcular<\/button><button type=\"reset\">Redefinir<\/button><\/div><div class=\"field is-checkbox hidden!\" id=\"field-auto-calc\"><input type=\"checkbox\" id=\"auto-calc\"><label for=\"auto-calc\">Calcular automaticamente<\/label><small>Se ativado, o resultado \u00e9 atualizado automaticamente quando voc\u00ea altera qualquer valor.<\/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> Resultados da lei de Kirchhoff<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Entalpia de rea\u00e7\u00e3o na temperatura-alvo (\u0394H\u2082)<\/span><span class=\"result-term\">\u0394H\u2082<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"kJ\/mol\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result is-column\" id=\"output-2\"><span class=\"field-title\"><span>\u0394Cp e unidades alternativas<\/span><\/span><span class=\"field-value\" id=\"result-2\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><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>Detalhes do c\u00e1lculo<\/span><\/span><span class=\"field-value\" id=\"result-3\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><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>Sobre a lei de Kirchhoff da termoqu\u00edmica<\/span><\/span><span class=\"field-value\" id=\"result-4\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><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\">Copiar link para este c\u00e1lculo<\/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>Deixar um coment\u00e1rio<\/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=\"2130\" aria-live=\"polite\" aria-labelledby=\"calc-reactions-title\"><p id=\"calc-reactions-title\" class=\"text-sm text-gray-500 text-center mb-2\">O que voc\u00ea achou deste resultado?<\/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\">Curti <\/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\">\u00datil <\/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\">Confuso <\/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\">Decepcionado <\/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\">Impreciso <\/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>F\u00f3rmula da lei de Kirchhoff da termoqu\u00edmica<\/h2><\/div>\r\n\t<figure class=\"not-prose formula\">\r\n\t\t<figcaption class=\"formula-title\">F\u00f3rmula<\/figcaption>\r\n\t\t<div class=\"text-base text-gray-800\" id=\"formula\">\n\\[ \\Delta H_2 = \\Delta H_1 + \\Delta C_p \\,(T_2 - T_1) \\\\ \\Delta C_p = \\sum_{\\text{produtos}} \\nu_i C_{p,i} - \\sum_{\\text{reagentes}} \\nu_i C_{p,i} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Onde:<\/strong><\/p>\n<ul>\n<li>\\(\\Delta H_1\\) \u2014 entalpia de rea\u00e7\u00e3o na temperatura de refer\u00eancia \\(T_1\\) (kJ\/mol)<\/li>\n<li>\\(\\Delta H_2\\) \u2014 entalpia de rea\u00e7\u00e3o na temperatura desejada \\(T_2\\) (kJ\/mol)<\/li>\n<li>\\(\\nu_i\\) \u2014 coeficiente estequiom\u00e9trico da esp\u00e9cie \\(i\\)<\/li>\n<li>\\(C_{p,i}\\) \u2014 capacidade t\u00e9rmica molar a press\u00e3o constante da esp\u00e9cie \\(i\\)<\/li>\n<li>\\(\\Delta C_p\\) \u2014 diferen\u00e7a entre as capacidades t\u00e9rmicas totais de produtos e reagentes<\/li>\n<\/ul>\n<p>A f\u00f3rmula mostra como a entalpia de rea\u00e7\u00e3o varia com a temperatura: aquecer (ou resfriar) reagentes e produtos pela mesma quantidade exige quantidades diferentes de calor, porque suas capacidades t\u00e9rmicas diferem, e essa diferen\u00e7a se acumula como o deslocamento em \\(\\Delta H\\). Ela assume que \\(\\Delta C_p\\) \u00e9 constante no intervalo \\(T_1\\)\u2013\\(T_2\\).<\/p>\n<p>\r\n<\/section>\n<style id=\"wpcoderpro-inline-2\">.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>Lei de Kirchhoff \u2013 Exemplo de c\u00e1lculo<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Exemplo:<\/strong> para a rea\u00e7\u00e3o de s\u00edntese da am\u00f4nia N\u2082 + 3H\u2082 \u2192 2NH\u2083, a entalpia padr\u00e3o de rea\u00e7\u00e3o a 298,15 K \u00e9 \u221292,2 kJ\/mol. Estime a entalpia a 400 K, usando \u03a3Cp(reagentes) = 115,5 J\/(mol\u00b7K) (29,1 + 3 \u00d7 28,8) e \u03a3Cp(produtos) = 71,2 J\/(mol\u00b7K) (2 \u00d7 35,6).<\/p>\n<p>\\[ \\Delta C_p = 71.2 - 115.5 = -44.3\\ \\text{J\/(mol\u00b7K)} = -0.0443\\ \\text{kJ\/(mol\u00b7K)} \\]<\/p>\n<p>\\[ \\Delta H_2 = -92.2 + (-0.0443)(400 - 298.15) = -92.2 - 4.51 = -96.71\\ \\text{kJ\/mol} \\]<\/p>\n<p><strong>Resultado:<\/strong> \u0394H\u2082 \u2248 \u221296,71 kJ\/mol. A 400 K, a rea\u00e7\u00e3o \u00e9 cerca de 4,5 kJ\/mol mais exot\u00e9rmica do que a 298,15 K, porque \u0394Cp \u00e9 negativo.<\/p>\n<p>\n\r\n<\/section>\n<h2>Como usar a calculadora<\/h2>\n<ol>\n<li>Informe a <strong>Entalpia de rea\u00e7\u00e3o na temperatura de refer\u00eancia (\u0394H\u2081)<\/strong> conhecida, escolhendo kJ\/mol ou kcal\/mol. Use um valor negativo para rea\u00e7\u00e3o exot\u00e9rmica e positivo para endot\u00e9rmica.<\/li>\n<li>Informe a <strong>Temperatura de refer\u00eancia (T\u2081)<\/strong> \u2014 normalmente 298,15 K \u2014 e selecione sua unidade (K, \u00b0C ou \u00b0F).<\/li>\n<li>Informe a <strong>Temperatura desejada (T\u2082)<\/strong> com sua unidade. \u00c9 a temperatura na qual voc\u00ea quer a entalpia ajustada.<\/li>\n<li>Para cada esp\u00e9cie da rea\u00e7\u00e3o, multiplique sua capacidade t\u00e9rmica molar \\(C_p\\) pelo seu coeficiente estequiom\u00e9trico e some os valores de cada lado da equa\u00e7\u00e3o. Informe os totais como <strong>Soma das capacidades t\u00e9rmicas dos reagentes (\u03a3Cp,reagentes)<\/strong> e <strong>Soma das capacidades t\u00e9rmicas dos produtos (\u03a3Cp,produtos)<\/strong>, selecionando J\/(mol\u00b7K), kJ\/(mol\u00b7K) ou cal\/(mol\u00b7K).<\/li>\n<li>Leia o resultado: a <strong>Entalpia de rea\u00e7\u00e3o na temperatura desejada (\u0394H\u2082)<\/strong> na unidade de entalpia escolhida, junto com \u0394Cp, convers\u00f5es de unidade e a resolu\u00e7\u00e3o completa passo a passo.<\/li>\n<\/ol>\n<h2>O que \u00e9 a lei de Kirchhoff da termoqu\u00edmica?<\/h2>\n<p>A lei de Kirchhoff descreve como a varia\u00e7\u00e3o de entalpia de uma rea\u00e7\u00e3o qu\u00edmica depende da temperatura. Como a entalpia \u00e9 uma fun\u00e7\u00e3o de estado, a derivada da entalpia de rea\u00e7\u00e3o em rela\u00e7\u00e3o \u00e0 temperatura, a press\u00e3o constante, \u00e9 igual \u00e0 diferen\u00e7a entre as capacidades t\u00e9rmicas de produtos e reagentes:<\/p>\n<p>\\[ \\left( \\frac{\\partial \\Delta H}{\\partial T} \\right)_p = \\Delta C_p \\]<\/p>\n<p>Integrando essa express\u00e3o de \\(T_1\\) a \\(T_2\\), obt\u00e9m-se \\(\\Delta H(T_2) = \\Delta H(T_1) + \\int_{T_1}^{T_2} \\Delta C_p\\, dT\\). Quando \\(\\Delta C_p\\) \u00e9 tratado como constante no intervalo de temperatura \u2014 uma boa aproxima\u00e7\u00e3o para faixas moderadas \u2014, a integral se simplifica para \\(\\Delta C_p (T_2 - T_1)\\), que \u00e9 a forma usada por esta calculadora.<\/p>\n<p>A interpreta\u00e7\u00e3o f\u00edsica \u00e9 simples. As entalpias de rea\u00e7\u00e3o tabeladas quase sempre se referem a 298,15 K, mas reatores, motores e calor\u00edmetros reais operam em outras temperaturas. Para comparar, imagine aquecer os reagentes de \\(T_1\\) a \\(T_2\\), deixar a rea\u00e7\u00e3o ocorrer e resfriar os produtos de volta \u2014 a diferen\u00e7a entre as duas demandas de calor \u00e9 exatamente \\(\\Delta C_p (T_2 - T_1)\\).<\/p>\n<p>Interpretar o sinal \u00e9 a parte mais \u00fatil. Se \\(\\Delta C_p &lt; 0\\) (os produtos t\u00eam capacidade t\u00e9rmica menor que os reagentes), a rea\u00e7\u00e3o se torna mais exot\u00e9rmica conforme a temperatura sobe. Se \\(\\Delta C_p &gt; 0\\), ela se torna mais endot\u00e9rmica. Se \\(\\Delta C_p = 0\\), a entalpia n\u00e3o depende da temperatura. Na pr\u00e1tica, \\(\\Delta C_p\\) costuma ser pequeno, de modo que \\(\\Delta H\\) geralmente se desloca apenas alguns por cento, mesmo em intervalos de centenas de kelvin.<\/p>\n<h2>Premissas, limita\u00e7\u00f5es e dicas pr\u00e1ticas<\/h2>\n<ul>\n<li><strong>Capacidades t\u00e9rmicas constantes.<\/strong> A forma linear \u00e9 precisa apenas em intervalos em que os valores de \\(C_p\\) mudam pouco. Para faixas amplas de temperatura (mais de algumas centenas de kelvin), use ajustes dependentes da temperatura, como \\(C_p = a + bT + cT^2\\) ou \\(C_p = a + bT + c\/T^2\\), de tabelas padr\u00e3o, e integre-os no lugar.<\/li>\n<li><strong>Sem mudan\u00e7as de fase.<\/strong> O c\u00e1lculo pressup\u00f5e que todas as esp\u00e9cies se mantenham na mesma fase entre \\(T_1\\) e \\(T_2\\). Uma fus\u00e3o, vaporiza\u00e7\u00e3o ou qualquer outra transi\u00e7\u00e3o dentro do intervalo acrescentaria um termo \\(\\nu \\Delta H_{\\text{transi\u00e7\u00e3o}}\\) na temperatura de transi\u00e7\u00e3o.<\/li>\n<li><strong>Dados coerentes.<\/strong> Todas as capacidades t\u00e9rmicas devem se referir \u00e0 mesma press\u00e3o (geralmente 1 bar) e ao mesmo estado f\u00edsico das esp\u00e9cies na equa\u00e7\u00e3o balanceada. Confira os coeficientes estequiom\u00e9tricos \u2014 as somas \u03a3\u03bdCp devem corresponder \u00e0 equa\u00e7\u00e3o como escrita.<\/li>\n<li><strong>Os sinais importam.<\/strong> Mantenha \u0394H\u2081 negativo para rea\u00e7\u00f5es exot\u00e9rmicas. A calculadora informa se a rea\u00e7\u00e3o \u00e9 exo- ou endot\u00e9rmica na temperatura desejada e de quanto a entalpia se deslocou.<\/li>\n<li><strong>Aten\u00e7\u00e3o a T\u2081 = T\u2082.<\/strong> Se as duas temperaturas forem iguais ap\u00f3s a convers\u00e3o para kelvin, \u0394H\u2082 simplesmente ser\u00e1 igual a \u0394H\u2081, e a calculadora pedir\u00e1 dois valores diferentes.<\/li>\n<\/ul>\n<p>Se voc\u00ea ainda n\u00e3o tem uma entalpia de refer\u00eancia, pode constru\u00ed-la a partir das entalpias padr\u00e3o de forma\u00e7\u00e3o com a <a href=\"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-lei-de-hess\/\">calculadora da Lei de Hess<\/a> ou estim\u00e1-la a partir das energias m\u00e9dias de liga\u00e7\u00e3o com a <a href=\"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-entalpia-reacao-energia-de-ligacao\/\">calculadora de entalpia de rea\u00e7\u00e3o por energias de liga\u00e7\u00e3o<\/a>. Para outras estimativas qu\u00edmicas dependentes da temperatura, a <a href=\"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-equacao-de-antoine\/\">calculadora da equa\u00e7\u00e3o de Antoine<\/a> \u00e9 uma boa companheira quando press\u00f5es de vapor est\u00e3o envolvidas.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Converta a entalpia de uma rea\u00e7\u00e3o de uma temperatura para outra usando a lei de Kirchhoff. Informe a entalpia conhecida na temperatura de refer\u00eancia, a temperatura desejada e as somas das capacidades t\u00e9rmicas de reagentes e produtos.<\/p>\n","protected":false},"author":3168,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[3],"tags":[67],"class_list":["post-2130","post","type-post","status-publish","format-standard","hentry","category-quimica","tag-reacoes"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2130","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/users\/3168"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/comments?post=2130"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2130\/revisions"}],"predecessor-version":[{"id":2614,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2130\/revisions\/2614"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/media?parent=2130"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/categories?post=2130"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/tags?post=2130"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}