{"id":2054,"date":"2026-10-14T09:01:33","date_gmt":"2026-10-14T08:01:33","guid":{"rendered":"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-area-superficial-bet\/"},"modified":"2026-10-14T09:01:33","modified_gmt":"2026-10-14T08:01:33","slug":"calculadora-area-superficial-bet","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-area-superficial-bet\/","title":{"rendered":"Calculadora de \u00c1rea Superficial BET"},"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\">Calcule a \u00e1rea superficial espec\u00edfica a partir da capacidade de monocamada BET<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"2054\" data-favorite-title=\"\u00c1rea superficial BET\" data-favorite-url=\"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-area-superficial-bet\/\" data-favorite-excerpt=\"Calcule a \u00e1rea superficial espec\u00edfica BET (m\u00b2\/g) de um p\u00f3 ou material poroso a partir da capacidade de monocamada, da \u00e1rea da se\u00e7\u00e3o transversal molecular e da massa da amostra. Aceita valores em mol, mmol ou cm\u00b3 (CNTP).\" aria-label=\"Adicionar aos favoritos\" data-favorite-icon=\"icon icon-molecule\">\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-area-superficial-bet\/\" method=\"POST\" class=\"calculator\" id=\"calculator-2054\" data-post=\"2054\"><fieldset class=\"fieldset-input is-2\"><legend class=\"sr-only\">Campos de entrada<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Quantidade de monocamada (nm)<\/label><div class=\"term\">nm<\/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=\"quantidade_de_monocamada_nm\" id=\"field-1\" aria-describedby=\"calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 22.5\" min=\"0\" value=\"22.5\"\/><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"unidade\" aria-label=\"Unidade\"><option value=\"mol\">mol<\/option><option value=\"mmol\">mmol<\/option><option value=\"umol\">\u00b5mol<\/option><option value=\"cm3_stp\" selected>cm\u00b3 (CNTP)<\/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\">Capacidade de monocamada nm obtida do gr\u00e1fico de BET (intercepto 1\/c). Os volumes de g\u00e1s referem-se a CNTP (0 \u00b0C, 1 atm), onde 1 mol = 22,414 cm\u00b3.<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-3\">\u00c1rea de se\u00e7\u00e3o transversal molecular (Am)<\/label><div class=\"term\">Am<\/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=\"rea_de_seo_transversal_molecular_am\" id=\"field-3\" aria-describedby=\"calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.162\" min=\"0\" value=\"0.162\"\/><div class=\"grid grid-cols-1\"><select id=\"field-4\" name=\"unidade\" aria-label=\"Unidade\"><option value=\"nm2\" selected>nm\u00b2<\/option><option value=\"A2\">\u00c5\u00b2<\/option><option value=\"pm2\">pm\u00b2<\/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\">\u00c1rea ocupada por mol\u00e9cula de adsorbato: N\u2082 a 77 K \u2248 0,162 nm\u00b2 (16,2 \u00c5\u00b2), Ar \u2248 0,142 nm\u00b2, Kr \u2248 0,195 nm\u00b2, CO\u2082 \u2248 0,170 nm\u00b2.<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-5\">Massa da amostra (m)<\/label><div class=\"term\">m<\/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=\"massa_da_amostra_m\" id=\"field-5\" aria-describedby=\"calc-info-5\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 1\" min=\"0\" value=\"1\"\/><div class=\"grid grid-cols-1\"><select id=\"field-6\" name=\"unidade\" aria-label=\"Unidade\"><option value=\"g\" selected>g<\/option><option value=\"mg\">mg<\/option><option value=\"kg\">kg<\/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\">Massa da amostra desgaseificada efetivamente colocada na c\u00e9lula BET.<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Recalcular\" id=\"calculate-button\" data-post=\"2054\">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 \u00e1rea superficial BET<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>\u00c1rea superficial espec\u00edfica (SBET)<\/span><span class=\"result-term\">SBET<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"m\u00b2\/g\"><\/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>\u00c1rea total e outras unidades<\/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 \u00e1rea superficial BET<\/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=\"2054\" 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>\u00c1rea superficial BET<\/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\\[ S_{BET} = \\frac{n_m \\cdot N_A \\cdot A_m}{m} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Onde:<\/strong><\/p>\n<ul>\n<li>\\(n_m\\) \u2014 capacidade de monocamada, a quantidade de g\u00e1s adsorvato que cobre toda a superf\u00edcie com exatamente uma camada de mol\u00e9culas (mol)<\/li>\n<li>\\(N_A\\) \u2014 constante de Avogadro, \\(6.02214076 \\times 10^{23}\\) mol\u207b\u00b9 (valor exato do SI)<\/li>\n<li>\\(A_m\\) \u2014 \u00e1rea da se\u00e7\u00e3o transversal molecular do adsorvato (m\u00b2 por mol\u00e9cula)<\/li>\n<li>\\(m\\) \u2014 massa da amostra desgaseificada (g)<\/li>\n<li>\\(S_{BET}\\) \u2014 \u00e1rea superficial espec\u00edfica (m\u00b2\/g)<\/li>\n<\/ul>\n<p>A f\u00f3rmula conta as mol\u00e9culas de uma monocamada compacta (\\(n_m \\cdot N_A\\)), multiplica pela \u00e1rea ocupada por cada mol\u00e9cula e divide pela massa da amostra, obtendo a \u00e1rea superficial por grama.<\/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>\u00c1rea superficial BET \u2013 Exemplo de c\u00e1lculo<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Exemplo:<\/strong> uma isoterma de adsor\u00e7\u00e3o de nitrog\u00eanio a 77 K em uma amostra de s\u00edlica de 1 g fornece um volume de monocamada de 22,5 cm\u00b3 (CNTP). Usando a \u00e1rea da se\u00e7\u00e3o transversal padr\u00e3o do N\u2082, \\(A_m\\) = 0,162 nm\u00b2, calcule a \u00e1rea superficial BET.<\/p>\n<p>Converta o volume de monocamada em mols usando o volume molar de um g\u00e1s ideal em CNTP (22,414 cm\u00b3\/mol, a mesma rela\u00e7\u00e3o usada na <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/avogadros-law-calculator\/\">lei de Avogadro<\/a>):<\/p>\n<p>\\[ n_m = \\frac{22.5 \\text{ cm}^3}{22{,}414 \\text{ cm}^3\/\\text{mol}} = 1.004 \\times 10^{-3} \\text{ mol} \\]<\/p>\n<p>Conte as mol\u00e9culas da monocamada e multiplique pela \u00e1rea de cada uma:<\/p>\n<p>\\[ N = 1.004 \\times 10^{-3} \\times 6.022 \\times 10^{23} = 6.045 \\times 10^{20} \\text{ mol\u00e9culas} \\]<\/p>\n<p>\\[ S = 6.045 \\times 10^{20} \\times 0.162 \\times 10^{-18} \\text{ m}^2 = 97.9 \\text{ m}^2 \\]<\/p>\n<p><strong>Resultado:<\/strong> \\( S_{BET} = 97.9 \/ 1 \\text{ g} \\approx 97.9 \\) m\u00b2\/g \u2014 um valor t\u00edpico para s\u00edlicas mesoporosas ou p\u00f3s de \u00f3xidos finos.<\/p>\n<p>\n\r\n<\/section>\n<h2>Como usar a calculadora de \u00e1rea superficial BET<\/h2>\n<ol>\n<li>Informe a <strong>quantidade de monocamada (nm)<\/strong> obtida a partir do seu gr\u00e1fico BET (o inverso do intercepto, \\(1\/c\\)) e escolha a unidade: <code>mol<\/code>, <code>mmol<\/code>, <code>\u00b5mol<\/code> ou <code>cm\u00b3 (CNTP)<\/code>. Os volumes de g\u00e1s devem se referir a CNTP (0 \u00b0C, 1 atm).<\/li>\n<li>Informe a <strong>\u00e1rea da se\u00e7\u00e3o transversal molecular (Am)<\/strong> do adsorvato e selecione <code>nm\u00b2<\/code>, <code>\u00c5\u00b2<\/code> ou <code>pm\u00b2<\/code>. O valor padr\u00e3o 0,162 nm\u00b2 \u00e9 o valor estabelecido para N\u2082 a 77 K.<\/li>\n<li>Informe a <strong>massa da amostra (m)<\/strong> desgaseificada na c\u00e9lula BET, em <code>g<\/code>, <code>mg<\/code> ou <code>kg<\/code>.<\/li>\n<li>Leia a <strong>\u00e1rea superficial espec\u00edfica (SBET)<\/strong> em m\u00b2\/g, junto com a \u00e1rea total da amostra, unidades alternativas e o c\u00e1lculo detalhado passo a passo.<\/li>\n<\/ol>\n<h2>O que \u00e9 \u00e1rea superficial BET?<\/h2>\n<p>O m\u00e9todo BET (Brunauer\u2013Emmett\u2013Teller) \u00e9 a t\u00e9cnica padr\u00e3o para medir a \u00e1rea superficial de s\u00f3lidos porosos ou finamente divididos \u2014 catalisadores, carv\u00f5es ativados, ze\u00f3litas, MOFs, pigmentos e p\u00f3s farmac\u00eauticos. A amostra \u00e9 resfriada, geralmente a 77 K, e um g\u00e1s \u00e9 adsorvido em sua superf\u00edcie a press\u00f5es relativas crescentes. A transforma\u00e7\u00e3o BET da isoterma, \\( p\/[v(p_0 - p)] \\) em fun\u00e7\u00e3o de \\( p\/p_0 \\), \u00e9 linear na faixa \\( p\/p_0 \\approx 0.05\\text{\u2013}0.30 \\); o intercepto e a inclina\u00e7\u00e3o dessa reta fornecem a capacidade de monocamada \\(n_m\\), ou seja, a quantidade de g\u00e1s necess\u00e1ria para cobrir toda a superf\u00edcie com exatamente uma camada de mol\u00e9culas.<\/p>\n<p>Conhecido \\(n_m\\), a \u00e1rea superficial segue diretamente: multiplicar pela constante de Avogadro conta as mol\u00e9culas da monocamada, e multiplicar pela \u00e1rea da se\u00e7\u00e3o transversal molecular \\(A_m\\) fornece a \u00e1rea total que essas mol\u00e9culas cobrem. Dividindo pela massa da amostra obt\u00e9m-se a \u00e1rea superficial espec\u00edfica \\(S_{BET}\\) em m\u00b2\/g, o n\u00famero quase sempre relatado na caracteriza\u00e7\u00e3o de materiais.<\/p>\n<p>Interpreta\u00e7\u00e3o do resultado: valores abaixo de ~10 m\u00b2\/g s\u00e3o considerados baixos (t\u00edpicos de p\u00f3s grosseiros e n\u00e3o porosos), 100\u2013500 m\u00b2\/g \u00e9 comum para s\u00edlicas e aluminas porosas, e acima de ~1000 m\u00b2\/g come\u00e7a o dom\u00ednio dos materiais altamente porosos, como carv\u00f5es ativados, ze\u00f3litas e estruturas metal-org\u00e2nicas. Como a \u00e1rea superficial governa a adsor\u00e7\u00e3o, a cat\u00e1lise e o comportamento de dissolu\u00e7\u00e3o, \\(S_{BET}\\) \u00e9 um par\u00e2metro essencial de controle de qualidade e pesquisa.<\/p>\n<h2>Escolhendo a \u00e1rea da se\u00e7\u00e3o transversal molecular<\/h2>\n<p>A precis\u00e3o do resultado depende fortemente do uso do \\(A_m\\) correto para o seu adsorvato e temperatura:<\/p>\n<table>\n<thead>\n<tr>\n<th>Adsorvato<\/th>\n<th>Temperatura<\/th>\n<th>Am (nm\u00b2)<\/th>\n<th>Am (\u00c5\u00b2)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>N\u2082 (padr\u00e3o)<\/td>\n<td>77 K<\/td>\n<td>0,162<\/td>\n<td>16,2<\/td>\n<\/tr>\n<tr>\n<td>Ar<\/td>\n<td>87 K<\/td>\n<td>0,142<\/td>\n<td>14,2<\/td>\n<\/tr>\n<tr>\n<td>Kr<\/td>\n<td>77 K<\/td>\n<td>0,195\u20130,210<\/td>\n<td>19,5\u201321,0<\/td>\n<\/tr>\n<tr>\n<td>CO\u2082<\/td>\n<td>273 K<\/td>\n<td>0,170<\/td>\n<td>17,0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>O nitrog\u00eanio a 77 K \u00e9 a escolha padr\u00e3o na maioria das an\u00e1lises de rotina. Para amostras de baixa \u00e1rea superficial (abaixo de ~10 m\u00b2\/g), prefere-se o cript\u00f4nio, pois sua press\u00e3o de satura\u00e7\u00e3o muito baixa reduz a incerteza da corre\u00e7\u00e3o de volume morto. O CO\u2082 a 273 K \u00e9 usado na an\u00e1lise de microporos porque alcan\u00e7a ultramicroporos em que o N\u2082 penetra lentamente a 77 K.<\/p>\n<h2>Premissas, limita\u00e7\u00f5es e dicas pr\u00e1ticas<\/h2>\n<ul>\n<li><strong>Monocamada compacta:<\/strong> o c\u00e1lculo assume que cada mol\u00e9cula ocupa sua \u00e1rea da se\u00e7\u00e3o transversal tabelada em uma camada compacta hexagonal. O empacotamento real pode se desviar disso, introduzindo incertezas de aproximadamente 5\u201320%.<\/li>\n<li><strong>Faixa de validade:<\/strong> o modelo BET s\u00f3 \u00e9 confi\u00e1vel na regi\u00e3o linear do gr\u00e1fico BET (\\(p\/p_0 \\approx 0.05\\text{\u2013}0.30\\)). Fora dessa faixa, a capacidade de monocamada \u2014 e portanto \\(S_{BET}\\) \u2014 torna-se n\u00e3o confi\u00e1vel.<\/li>\n<li><strong>Microporos:<\/strong> em poros mais estreitos que ~2 nm o conceito de monocamada perde validade, pois o preenchimento de poros compete com a adsor\u00e7\u00e3o em multicamadas. Para materiais fortemente microporosos, relate \\(S_{BET}\\) junto com os volumes de microporo obtidos por an\u00e1lise t-plot ou DFT.<\/li>\n<li><strong>Desgaseifica\u00e7\u00e3o:<\/strong> a amostra deve ser completamente desgaseificada antes da medi\u00e7\u00e3o, para que toda a superf\u00edcie fique acess\u00edvel ao adsorvato; \u00e1gua residual ou contaminantes fazem o resultado ficar abaixo do valor real.<\/li>\n<li><strong>Conven\u00e7\u00e3o CNTP:<\/strong> se voc\u00ea informar a quantidade de monocamada como volume de g\u00e1s, ele deve estar corrigido para CNTP (0 \u00b0C, 1 atm), onde 1 mol ocupa 22,414 cm\u00b3. Instrumentos que relatam volumes em outras condi\u00e7\u00f5es exigem convers\u00e3o pr\u00e9via \u2014 as mesmas rela\u00e7\u00f5es de g\u00e1s ideal usadas nas calculadoras de <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/gas-density-calculator\/\">densidade de g\u00e1s<\/a> e <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/molecular-speed-of-a-gas-calculator\/\">velocidade molecular<\/a>.<\/li>\n<\/ul>\n<p>Para controle de qualidade, registre sempre, junto com \\(S_{BET}\\), o adsorvato, a temperatura, o valor de \\(A_m\\), a faixa de press\u00e3o relativa e a constante C do ajuste BET, pois esses detalhes determinam se resultados de laborat\u00f3rios diferentes s\u00e3o compar\u00e1veis.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calcule a \u00e1rea superficial espec\u00edfica BET (m\u00b2\/g) de um p\u00f3 ou material poroso a partir da capacidade de monocamada, da \u00e1rea da se\u00e7\u00e3o transversal molecular e da massa da amostra. Aceita valores em mol, mmol ou cm\u00b3 (CNTP).<\/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":[23],"class_list":["post-2054","post","type-post","status-publish","format-standard","hentry","category-quimica","tag-ligacoes-quimicas"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2054","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=2054"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2054\/revisions"}],"predecessor-version":[{"id":2651,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2054\/revisions\/2651"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/media?parent=2054"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/categories?post=2054"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/tags?post=2054"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}