{"id":2091,"date":"2026-10-14T19:20:28","date_gmt":"2026-10-14T18:20:28","guid":{"rendered":"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-coeficiente-atividade-debye-huckel\/"},"modified":"2026-10-14T19:20:28","modified_gmt":"2026-10-14T18:20:28","slug":"calculadora-coeficiente-atividade-debye-huckel","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-coeficiente-atividade-debye-huckel\/","title":{"rendered":"Calculadora do coeficiente de atividade de Debye\u2013H\u00fcckel"},"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\">Estime o coeficiente de atividade de um \u00edon a partir da for\u00e7a i\u00f4nica<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"2091\" data-favorite-title=\"Coeficiente de atividade de Debye\u2013H\u00fcckel\" data-favorite-url=\"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-coeficiente-atividade-debye-huckel\/\" data-favorite-excerpt=\"Estime o coeficiente de atividade de um \u00edon em solu\u00e7\u00e3o aquosa usando a lei limite de Debye\u2013H\u00fcckel, a equa\u00e7\u00e3o estendida ou a equa\u00e7\u00e3o de Davies. Informe a for\u00e7a i\u00f4nica, a carga do \u00edon e a temperatura para obter \u03b3 e log\u2081\u2080 \u03b3.\" aria-label=\"Adicionar aos favoritos\" data-favorite-icon=\"icon icon-chemistry\">\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-coeficiente-atividade-debye-huckel\/\" method=\"POST\" class=\"calculator\" id=\"calculator-2091\" data-post=\"2091\"><fieldset class=\"fieldset-input is-2\"><legend class=\"sr-only\">Campos de entrada<\/legend><div class=\"field is-single\" id=\"input-1\"><label for=\"field-1\">Modelo<\/label><div class=\"grid grid-cols-1\"><select id=\"field-1\" name=\"modelo\"><option value=\"limiting\">Lei limite de Debye\u2013H\u00fcckel (I \u2264 0,01 M)<\/option><option value=\"extended\">Equa\u00e7\u00e3o estendida de Debye\u2013H\u00fcckel (I \u2264 0,1 M)<\/option><option value=\"davies\" selected>Equa\u00e7\u00e3o de Davies (I \u2264 0,5 M)<\/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 has-term\" id=\"input-2\"><label for=\"field-2\">For\u00e7a i\u00f4nica (I)<\/label><div class=\"term\">I<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"fora_inica_i\" id=\"field-2\" aria-describedby=\"calc-unit-2 calc-info-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.1\" min=\"0\" value=\"0.1\"\/><div class=\"unit\" id=\"calc-unit-2\">mol\/L<\/div><small id=\"calc-info-2\">I = \u00bd \u03a3 c\u1d62z\u1d62\u00b2 somado sobre todos os \u00edons da solu\u00e7\u00e3o.<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-3\">Carga do \u00edon (z)<\/label><div class=\"term\">z<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"number\" name=\"carga_do_on_z\" id=\"field-3\" aria-describedby=\"calc-info-3\" placeholder=\"ex.: 1, 2 ou \u22122\" step=\"any\" value=\"1\"\/><small id=\"calc-info-3\">Carga do \u00edon cujo coeficiente de atividade voc\u00ea deseja, por exemplo +1 para Na\u207a, \u22122 para SO\u2084\u00b2\u207b. Apenas z\u00b2 \u00e9 usado, ent\u00e3o o sinal n\u00e3o importa.<\/small><\/div><div class=\"field is-single\" id=\"input-4\"><label for=\"field-4\">Temperatura da \u00e1gua<\/label><div class=\"grid grid-cols-1\"><select id=\"field-4\" name=\"temperatura_da_gua\"><option value=\"t0\">0 \u00b0C<\/option><option value=\"t10\">10 \u00b0C<\/option><option value=\"t20\">20 \u00b0C<\/option><option value=\"t25\" selected>25 \u00b0C<\/option><option value=\"t30\">30 \u00b0C<\/option><option value=\"t40\">40 \u00b0C<\/option><option value=\"t50\">50 \u00b0C<\/option><option value=\"custom\">Constantes A e B personalizadas<\/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 has-term\" id=\"input-5\" hidden><label for=\"field-5\">Constante A<\/label><div class=\"term\">A<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"constante_a\" id=\"field-5\" aria-describedby=\"calc-info-5\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.509\" min=\"0\" value=\"0.509\"\/><small id=\"calc-info-5\">Constante A de Debye\u2013H\u00fcckel para o seu solvente e temperatura (0,509 para a \u00e1gua a 25 \u00b0C).<\/small><\/div><div class=\"field has-term\" id=\"input-6\" hidden><label for=\"field-6\">Constante B<\/label><div class=\"term\">B<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"constante_b\" id=\"field-6\" aria-describedby=\"calc-info-6\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.328\" min=\"0\" value=\"0.328\"\/><small id=\"calc-info-6\">Constante B de Debye\u2013H\u00fcckel para o seu solvente e temperatura (0,328 para a \u00e1gua a 25 \u00b0C).<\/small><\/div><div class=\"field has-term\" id=\"input-7\" hidden><label for=\"field-7\">Par\u00e2metro de tamanho i\u00f4nico (a)<\/label><div class=\"term\">a<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"parmetro_de_tamanho_inico_a\" id=\"field-7\" aria-describedby=\"calc-unit-7 calc-info-7\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 4\" min=\"0\" value=\"4\"\/><div class=\"unit\" id=\"calc-unit-7\">\u00c5<\/div><small id=\"calc-info-7\">Di\u00e2metro efetivo do \u00edon hidratado na equa\u00e7\u00e3o estendida: \u2248 3 \u00c5 para K\u207a\/Cl\u207b\/NO\u2083\u207b, 4\u20135 \u00c5 para Na\u207a\/Ca\u00b2\u207a, at\u00e9 9\u201311 \u00c5 para H\u207a\/Mg\u00b2\u207a.<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Recalcular\" id=\"calculate-button\" data-post=\"2091\">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 do coeficiente de atividade<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Coeficiente de atividade (\u03b3)<\/span><span class=\"result-term\">\u03b3<\/span><\/span><span class=\"field-value\" id=\"result-1\"><\/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\" id=\"output-2\"><span class=\"field-title\"><span>log\u2081\u2080 \u03b3<\/span><span class=\"result-term\">log \u03b3<\/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>Faixa de validade e aplicabilidade do modelo<\/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>Detalhes do c\u00e1lculo<\/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 class=\"field-result is-column\" id=\"output-5\"><span class=\"field-title\"><span>Sobre a teoria de Debye\u2013H\u00fcckel<\/span><\/span><span class=\"field-value\" id=\"result-5\"><\/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=\"2091\" 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 do coeficiente de atividade de Debye\u2013H\u00fcckel<\/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\">\\[ \\log_{10}\\gamma = -A z^2 \\sqrt{I} \\qquad \\text{(lei limite)} \\\\[4pt] \\log_{10}\\gamma = \\frac{-A z^2 \\sqrt{I}}{1 + B a \\sqrt{I}} \\qquad \\text{(estendida)} \\\\[4pt] \\log_{10}\\gamma = -A z^2 \\left( \\frac{\\sqrt{I}}{1+\\sqrt{I}} - 0.3\\,I \\right) \\qquad \\text{(Davies)} \\]\n\\[ \\gamma = 10^{\\log_{10}\\gamma} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Em que:<\/strong><\/p>\n<ul>\n<li>\\(\\gamma\\) \u2014 coeficiente de atividade do \u00edon (adimensional)<\/li>\n<li>\\(z\\) \u2014 carga do \u00edon (s\u00f3 \\(z^2\\) entra no c\u00e1lculo, portanto o sinal n\u00e3o importa)<\/li>\n<li>\\(I\\) \u2014 for\u00e7a i\u00f4nica da solu\u00e7\u00e3o em mol\/L, \\(I = \\tfrac{1}{2}\\sum c_i z_i^2\\)<\/li>\n<li>\\(A\\), \\(B\\) \u2014 constantes de Debye\u2013H\u00fcckel do solvente, definidas pela temperatura (0,509 e 0,328 para a \u00e1gua a 25 \u00b0C)<\/li>\n<li>\\(a\\) \u2014 par\u00e2metro de tamanho i\u00f4nico em \u00e5ngstr\u00f6ms (apenas na equa\u00e7\u00e3o estendida)<\/li>\n<\/ul>\n<p>Cada variante fornece o logaritmo na base 10 do coeficiente de atividade; elevando 10 a essa pot\u00eancia obt\u00e9m-se o pr\u00f3prio \\(\\gamma\\), que converte uma concentra\u00e7\u00e3o anal\u00edtica em uma atividade termodin\u00e2mica efetiva por meio de \\(a = \\gamma c\\).<\/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>Coeficiente de atividade de Debye\u2013H\u00fcckel \u2013 Exemplo de c\u00e1lculo<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Exemplo:<\/strong> estime o coeficiente de atividade do Na\u207a (z = +1) em uma solu\u00e7\u00e3o de for\u00e7a i\u00f4nica 0,1 M a 25 \u00b0C, usando a equa\u00e7\u00e3o de Davies.<\/p>\n<p>\\[ \\sqrt{I} = \\sqrt{0.1} = 0.3162 \\]<\/p>\n<p>\\[ \\frac{\\sqrt{I}}{1+\\sqrt{I}} - 0.3I = \\frac{0.3162}{1.3162} - 0.3(0.1) = 0.2403 - 0.0300 = 0.2103 \\]<\/p>\n<p>\\[ \\log_{10}\\gamma = -0.509 \\times 1^2 \\times 0.2103 = -0.1070 \\]<\/p>\n<p>\\[ \\gamma = 10^{-0.1070} = 0.782 \\]<\/p>\n<p><strong>Resultado:<\/strong> \u03b3 \u2248 0,782 (log\u2081\u2080 \u03b3 \u2248 \u22120,107). A concentra\u00e7\u00e3o efetiva do Na\u207a corresponde a apenas cerca de 78% da concentra\u00e7\u00e3o anal\u00edtica \u2014 uma corre\u00e7\u00e3o consider\u00e1vel a 0,1 M.<\/p>\n<p>\n\r\n<\/section>\n<h2>Como usar a calculadora<\/h2>\n<ol>\n<li>Escolha o <strong>Modelo<\/strong>: a lei limite para I at\u00e9 0,01 M, a equa\u00e7\u00e3o estendida de Debye\u2013H\u00fcckel at\u00e9 0,1 M ou a equa\u00e7\u00e3o de Davies at\u00e9 0,5 M quando o par\u00e2metro de tamanho i\u00f4nico n\u00e3o \u00e9 conhecido.<\/li>\n<li>Digite a <strong>For\u00e7a i\u00f4nica (I)<\/strong> em mol\/L. Se voc\u00ea s\u00f3 conhece a composi\u00e7\u00e3o, calcule antes \\(I = \\tfrac{1}{2}\\sum c_i z_i^2\\) somando sobre todos os \u00edons.<\/li>\n<li>Informe a <strong>Carga do \u00edon (z)<\/strong> em quest\u00e3o, por exemplo 2 para Ca\u00b2\u207a ou \u22122 para SO\u2084\u00b2\u207b. O sinal \u00e9 indiferente, pois apenas \\(z^2\\) entra nas equa\u00e7\u00f5es.<\/li>\n<li>Selecione a <strong>Temperatura da \u00e1gua<\/strong> (0\u201350 \u00b0C) para definir automaticamente as constantes A e B, ou escolha \"Constantes A e B personalizadas\" e digite-as para outro solvente.<\/li>\n<li>Se voc\u00ea escolheu a equa\u00e7\u00e3o estendida, informe o <strong>Par\u00e2metro de tamanho i\u00f4nico (a)<\/strong> em \u00e5ngstr\u00f6ms \u2014 cerca de 3 \u00c5 para K\u207a, Cl\u207b, NO\u2083\u207b; 4\u20135 \u00c5 para Na\u207a ou Ca\u00b2\u207a; e at\u00e9 9\u201311 \u00c5 para H\u207a ou Mg\u00b2\u207a.<\/li>\n<li>Leia o <strong>Coeficiente de atividade (\u03b3)<\/strong> e o <strong>log\u2081\u2080 \u03b3<\/strong> nos resultados, junto com a faixa de validade e a substitui\u00e7\u00e3o passo a passo.<\/li>\n<\/ol>\n<h2>O que \u00e9 o coeficiente de atividade de Debye\u2013H\u00fcckel?<\/h2>\n<p>Em qualquer solu\u00e7\u00e3o que n\u00e3o seja extremamente dilu\u00edda, cada \u00edon est\u00e1 cercado por uma <em>atmosfera i\u00f4nica<\/em> de carga oposta. Essa nuvem blinda as intera\u00e7\u00f5es eletrost\u00e1ticas do \u00edon, de modo que ele se comporta, do ponto de vista termodin\u00e2mico, como se sua concentra\u00e7\u00e3o fosse menor que o valor medido analiticamente. Essa concentra\u00e7\u00e3o efetiva \u00e9 chamada de <strong>atividade<\/strong>, \\(a = \\gamma c\\), e o fator de proporcionalidade \\(\\gamma\\) \u00e9 o <strong>coeficiente de atividade<\/strong>. A teoria de Debye\u2013H\u00fcckel deduz \\(\\gamma\\) puramente a partir da eletrost\u00e1tica: a corre\u00e7\u00e3o cresce com o quadrado da carga do \u00edon e com a raiz quadrada da for\u00e7a i\u00f4nica da solu\u00e7\u00e3o.<\/p>\n<p>Os coeficientes de atividade importam sempre que constantes de equil\u00edbrio s\u00e3o aplicadas a solu\u00e7\u00f5es reais. Um <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/solubility-product-ksp-calculator\/\">produto de solubilidade<\/a> \u00e9 escrito em atividades, e n\u00e3o em concentra\u00e7\u00f5es, de modo que um sal pode parecer muito mais sol\u00favel em um meio com 0,1 M de NaCl do que em \u00e1gua pura simplesmente porque \u03b3 diminui. A mesma corre\u00e7\u00e3o aparece em <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/standard-cell-potential-calculator\/\">potenciais de c\u00e9lula previstos pela equa\u00e7\u00e3o de Nernst<\/a> e em <a href=\"https:\/\/wpcalc.com\/pt\/quimica\/calculadora-equacao-van-t-hoff\/\">c\u00e1lculos de deslocamento de equil\u00edbrio<\/a>: ignorar \u03b3 \u00e9 a fonte mais comum de erro ao comparar valores medidos e previstos em solu\u00e7\u00f5es moderadamente concentradas.<\/p>\n<p>As tr\u00eas variantes da teoria equilibram precis\u00e3o e dados necess\u00e1rios. A <strong>lei limite<\/strong> \u00e9 exata apenas quando I \u2192 0 e n\u00e3o exige nada al\u00e9m de I e z. A <strong>equa\u00e7\u00e3o estendida<\/strong> acrescenta o tamanho finito do \u00edon \\(a\\), estendendo a faixa confi\u00e1vel at\u00e9 cerca de 0,1 M. A <strong>equa\u00e7\u00e3o de Davies<\/strong> substitui \\(a\\) por um termo emp\u00edrico \u22120,3I, de modo que dispensa o par\u00e2metro de tamanho e continua \u00fatil at\u00e9 aproximadamente 0,5 M \u2014 por isso \u00e9 a escolha padr\u00e3o em geoqu\u00edmica e em softwares de especia\u00e7\u00e3o. A calculadora avisa claramente quando a sua for\u00e7a i\u00f4nica ultrapassa a faixa recomendada do modelo escolhido.<\/p>\n<p>Para interpretar o resultado: \u03b3 = 1 significa que o \u00edon se comporta idealmente (na pr\u00e1tica, apenas na dilui\u00e7\u00e3o infinita); \u03b3 = 0,782, como no exemplo, significa que a atividade do \u00edon equivale a 78% da concentra\u00e7\u00e3o anal\u00edtica. Como \\(z^2\\) aparece em todas as f\u00f3rmulas, os \u00edons divalentes s\u00e3o corrigidos cerca de quatro vezes mais fortemente que os monovalentes na mesma for\u00e7a i\u00f4nica.<\/p>\n<h2>Pressupostos, limita\u00e7\u00f5es e dicas pr\u00e1ticas<\/h2>\n<ul>\n<li><strong>Apenas solu\u00e7\u00f5es dilu\u00eddas.<\/strong> A teoria trata o solvente como um cont\u00ednuo diel\u00e9trico com \u00edons puntiformes (na lei limite) ou de tamanho fixo. Acima dos limites indicados, o pareamento de \u00edons, as intera\u00e7\u00f5es espec\u00edficas \u00edon\u2013solvente e as concentra\u00e7\u00f5es finitas de \u00edons passam a dominar; s\u00e3o ent\u00e3o necess\u00e1rios modelos SIT ou Pitzer.<\/li>\n<li>Assume-se <strong>dissocia\u00e7\u00e3o completa<\/strong>. Eletr\u00f3litos fracos devem ser especiados antes \u2014 s\u00f3 os \u00edons livres contribuem para I e para o \u03b3 de um dado \u00edon.<\/li>\n<li><strong>\u00c1gua como solvente.<\/strong> As constantes A e B embutidas valem para a \u00e1gua entre 0 e 50 \u00b0C. Para outros solventes, procure os valores de A e B desse meio e use a op\u00e7\u00e3o \"Constantes A e B personalizadas\".<\/li>\n<li><strong>Molaridade vs. molalidade.<\/strong> As equa\u00e7\u00f5es s\u00e3o definidas rigorosamente na escala molal; a diferen\u00e7a em rela\u00e7\u00e3o \u00e0 molaridade \u00e9 desprez\u00edvel abaixo de \u2248 0,5 M, o que coincide com a faixa de validade dos modelos.<\/li>\n<li><strong>Dica:<\/strong> se voc\u00ea n\u00e3o conhece o par\u00e2metro de tamanho i\u00f4nico do seu \u00edon, use a equa\u00e7\u00e3o de Davies \u2014 ela foi criada justamente para dispensar esse dado.<\/li>\n<li><strong>Dica:<\/strong> para montar I voc\u00ea mesmo, some sobre todos os \u00edons da solu\u00e7\u00e3o: para 0,01 M de MgCl\u2082, \\(I = \\tfrac{1}{2}(0.01 \\times 2^2 + 0.02 \\times 1^2) = 0.03\\) M.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Estime o coeficiente de atividade de um \u00edon em solu\u00e7\u00e3o aquosa usando a lei limite de Debye\u2013H\u00fcckel, a equa\u00e7\u00e3o estendida ou a equa\u00e7\u00e3o de Davies. Informe a for\u00e7a i\u00f4nica, a carga do \u00edon e a temperatura para obter \u03b3 e log\u2081\u2080 \u03b3.<\/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":[71],"class_list":["post-2091","post","type-post","status-publish","format-standard","hentry","category-quimica","tag-estequiometria"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2091","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=2091"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2091\/revisions"}],"predecessor-version":[{"id":2473,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/2091\/revisions\/2473"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/media?parent=2091"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/categories?post=2091"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/tags?post=2091"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}