{"id":7186,"date":"2023-10-24T13:55:17","date_gmt":"2023-10-24T11:55:17","guid":{"rendered":"https:\/\/www.em-grade.com\/sin-categorizar\/definicion-de-ph-ka-y-pka\/"},"modified":"2025-05-16T15:18:35","modified_gmt":"2025-05-16T13:18:35","slug":"definicion-de-ph-ka-y-pka","status":"publish","type":"post","link":"https:\/\/www.em-grade.com\/es\/definiciones-quimica\/definicion-de-ph-ka-y-pka\/","title":{"rendered":"Definici\u00f3n de pH, Ka y Pka"},"content":{"rendered":"

Definici\u00f3n del pKa<\/h4>\n

A partir de la constante de acidez Ka, se define el pKa de la siguiente manera:<\/p>\n

pKa<\/span><\/span>=<\/span><\/span>\u2212<\/span>log<\/span>(<\/span>Ka<\/span><\/span>)<\/span><\/span><\/span><\/span><\/span><\/strong><\/p>\n

Generalmente se utiliza el pKa en lugar del Ka para calificar la fuerza de un \u00e1cido.<\/p>\n

Cuanto m\u00e1s fuerte es el \u00e1cido, m\u00e1s bajo es su pKa.<\/strong>
\nEsto se debe a que un \u00e1cido fuerte est\u00e1 muy disociado: la concentraci\u00f3n del \u00e1cido no disociado [<\/span>A<\/span>H<\/span>]<\/span><\/span><\/span><\/span> se vuelve muy baja.<\/p>\n

\n

Relaci\u00f3n entre pKa, pH y fuerzas \u00e1cidas<\/h4>\n

Partimos de la f\u00f3rmula del Ka para un par \u00e1cido-base:<\/p>\n

Ka<\/span><\/span>=<\/span><\/span>[<\/span>AH<\/span>]<\/span>[<\/span>H<\/span>+<\/span><\/span><\/span><\/span>]<\/span>[<\/span>A<\/span>\u2212<\/span><\/span><\/span><\/span>]<\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/strong><\/p>\n

Al tomar el logaritmo decimal en ambos lados, se obtiene:<\/p>\n

\u2212<\/span>log<\/span>(<\/span>Ka<\/span><\/span>)<\/span>=<\/span><\/span>\u2212<\/span>log<\/span>([<\/span>H<\/span>+<\/span><\/span><\/span><\/span><\/span><\/span><\/span>])<\/span>\u2212<\/span><\/span>log<\/span>(<\/span><\/span>[<\/span>AH<\/span>]<\/span>[<\/span>A<\/span>\u2212<\/span><\/span><\/span><\/span>]<\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span>)<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/strong><\/p>\n

As\u00ed, se reconocen los siguientes t\u00e9rminos:<\/p>\n

    \n
  • pKa<\/span><\/span>=<\/span><\/span>\u2212<\/span>log<\/span>(<\/span>Ka<\/span><\/span>)<\/span><\/span><\/span><\/span><\/li>\n
  • pH<\/span><\/span>=<\/span><\/span>\u2212<\/span>log<\/span>([<\/span>H<\/span>+<\/span><\/span><\/span><\/span><\/span><\/span><\/span>])<\/span><\/span><\/span><\/span><\/li>\n<\/ul>\n

    Lo que nos da la relaci\u00f3n:<\/p>\n

    pKa<\/span><\/span>=<\/span><\/span>pH<\/span><\/span>\u2212<\/span><\/span>log<\/span>(<\/span><\/span>[<\/span>AH<\/span>]<\/span>[<\/span>A<\/span>\u2212<\/span><\/span><\/span><\/span>]<\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span>)<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/strong><\/p>\n

    \n

    Definici\u00f3n pr\u00e1ctica del pH en funci\u00f3n del pKa<\/h4>\n

    Reordenando la f\u00f3rmula anterior, obtenemos la expresi\u00f3n bien conocida:<\/p>\n

    pH<\/span><\/span>=<\/span><\/span>pKa<\/span><\/span>+<\/span><\/span>log<\/span>(<\/span><\/span>[<\/span>AH<\/span>]<\/span>[<\/span>A<\/span>\u2212<\/span><\/span><\/span><\/span>]<\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span>)<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/strong><\/p>\n

    Donde
    \n[<\/span>A<\/span>\u2212<\/span><\/span><\/span><\/span><\/span><\/span><\/span>]<\/span>:<\/span><\/span><\/span><\/span> concentraci\u00f3n de la base conjugada;
    \n[<\/span>AH<\/span><\/span>]<\/span>:<\/span><\/span><\/span><\/span> concentraci\u00f3n de la forma \u00e1cida.<\/p>\n

    \ud83d\udca1 Esta ecuaci\u00f3n, tambi\u00e9n llamada ecuaci\u00f3n de Henderson-Hasselbalch<\/strong>, es fundamental para entender los tampones y la fuerza \u00e1cida\/base en qu\u00edmica y biolog\u00eda.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

    Definici\u00f3n del pKa A partir de la constante de acidez Ka, se define el pKa de la siguiente manera: pKa=\u2212log(Ka) Generalmente se utiliza el pKa en lugar del Ka para…<\/p>\n","protected":false},"author":8,"featured_media":7187,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","_seopress_robots_follow":"","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"","_seopress_social_fb_title":"","_seopress_social_fb_desc":"","_seopress_social_fb_img":"","_seopress_social_fb_img_attachment_id":0,"_seopress_social_fb_img_width":0,"_seopress_social_fb_img_height":0,"_seopress_social_twitter_title":"","_seopress_social_twitter_desc":"","_seopress_social_twitter_img":"","_seopress_social_twitter_img_attachment_id":0,"_seopress_social_twitter_img_width":0,"_seopress_social_twitter_img_height":0,"_seopress_redirections_value":"","_seopress_redirections_enabled":"","_seopress_redirections_enabled_regex":"","_seopress_redirections_logged_status":"","_seopress_redirections_param":"","_seopress_redirections_type":0,"_seopress_analysis_target_kw":"","_seopress_news_disabled":"","_seopress_video_disabled":"","_seopress_video":[],"_seopress_pro_schemas_manual":[],"_seopress_pro_rich_snippets_disable_all":"","_seopress_pro_rich_snippets_disable":[],"_seopress_pro_schemas":[],"itsec_x_frame_options":"","footnotes":""},"categories":[453],"tags":[],"class_list":["post-7186","post","type-post","status-publish","format-standard","has-post-thumbnail","category-definiciones-quimica"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/posts\/7186","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/comments?post=7186"}],"version-history":[{"count":2,"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/posts\/7186\/revisions"}],"predecessor-version":[{"id":11115,"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/posts\/7186\/revisions\/11115"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/media\/7187"}],"wp:attachment":[{"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/media?parent=7186"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/categories?post=7186"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.em-grade.com\/es\/wp-json\/wp\/v2\/tags?post=7186"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}