• 2022-06-26
    如何计算酸式盐溶液的pH?
  • 酸式盐(MHA)在溶液中既能解离也会水解,溶液中存在如下平衡:[tex=20.071x2.929]hEhheiLzAZ5XED+y0dmi8I2PnYznXYrG1NzRgZOlyajaN5oF2UlsJJ3FTi9uOgmJLLSg8EfcAatbOq/vCfFBRUsxpaUbWXmN+iGdtJl2fUotU7TbyRksG4SPRfTlsJvykSKz77ZWRUpVKoszz91y2U/VQLY9A69o5+xLzKw+iqs/MA6El4keLrPkdMbrZpEjjAPHNIjNlOaudKO0VDFsGA==[/tex][tex=27.5x2.786]12iFEaMhIIWCq9BUenqL0jSvvUppenDBnIRhbB25yUWn6h8zAAVsaBmtO7aapn8H6uGTcLs91RCfWKFz390tbPnvT6WboN00uGbGz+PGr3I5m50fbEYcQjYyXX1IQRgGjJRV6MPJlAXaZHFE7XfUcCsxMWyuSYBspDsEX9ciYKZ6lUm//BfYG6gkrTnkKNQq03Zbd/2oJt+clGUAA02Tj7rJJlAA4cfusJhrxakmcm/xwyoRco5FJozeODcWhJLrHGuRCX/OAyVOMZC0q3gXKvbyTGjuOdcJsj65luvG6Hs=[/tex][tex=23.857x1.714]WYSBbZQ3mcDsk9cu0hr6AY0iCduJk72jZXoQ5Tv00+0PTAZetP3cacCOTFgptXoH116ZMY88aFUiLdvR/vo44aENJnjoM/i6oP7YtPLfJvi5M2DGtWCYkVPzQoBqcySLBR44y9k3uKFPN6K3JI6qwG0ASPsTQICAYdHN47ub49QoUg22ifIaUIlERtFKvW7ZuOMMtBblhb9uJAM+csgRcA==[/tex]可见,平衡体系中存在[tex=10.643x1.429]Q72MJxToCE9dclCdJANykx4u10eDEi7boK3DUAdKR4GAAseM9TSqUgYYNeorsgFH[/tex], 当达到平衡时,溶液中这 5 种物种的浓度均是未知的,所以,要建立 5 个联立方程才能导出[tex=3.071x1.5]xIbhfnA4ko32sgGHET4h2Cg7ORVeaqW733f3JR7SEk4=[/tex] 的计算式 在浓度为[tex=0.786x1.0]/k3X7jc3aTSkZNIWBI8xLQ==[/tex]的 MHA 溶液中,物料平衡:[tex=19.5x1.571]XLiQxt0u1Wg4JzphLY7MwPdBjpOLv4Pp4G/R0RnNgFKlzdWJ4+d5ZiTiQXl7/C+sHaY8UoiQzQIVR65g9djkWIh2TcUIfrCoP6q9uhtu4kYac4NNy2Bc8CyeS9Zmonm7HYQAGCxCHb2jFiSmOXd9mg==[/tex]电荷平衡:[tex=23.929x1.571]esYVsraZkRsRRQoZ0IfApm9KZSBELo90Uy3NzMEsdpA+opyxqB1vr6THCeZ4yomRuRpEZXcY4OvI6GlPALrcie68tl2kJra0FwpuSg15qaTcFrIKVO8EQSHKpRPoLu1Ya4c0OLTFrhkqgjDS2N3n+iDpUkMIPeRyj8abDVwiPpXm1FptBI2D8/fdspcu5nqz[/tex]体系中:[tex=8.5x1.5]oYEwj+zljugjymXDfiyJLk1W3kgkEJAxep6J+9tw6NvgZyxpUZwq5WzOWHI+Iiaafb1B6V5bp2OhNdRdrEn5dQ==[/tex]将式(4)代人式(5)得[tex=16.071x1.571]DOfi8XhWXZeazqGBfg6MqyJ8GkU/CdLMqx51nsxK0RT8W7SUfU9p+50NtIJAHHUKcgtDcG1xA4LbgFQ0JhGcT7WsufPwgkDzcM0LWDbvlD8/MNCrANqhEIwTWbrdO1U/[/tex][tex=13.857x1.571]Mz13nG+MluBRPxXB4NjDYi6+VKEHnAkMOeKu1gnR/uVjFUCwsC9jdw82aGm+AbF9KMoYlv1j5QLr/KJcRjY3kVxzqxontRneVjM7DckGNzQ=[/tex]整理得[tex=16.143x1.571]PiJi8RZrWp/F+qta1DeRrUxPGixeP9OJhPo+d/dI9eAVGs5lP12PIbvUHsJ0um/HfZPmAVPcxsAl0422zcyVu7RjxYE1mlYqxcEMtWUZOVzpRDXrdPgcY0bnlKkcL9g+[/tex]再利用式(1)~式(3)三个平衡关系式,得[tex=24.357x2.857]PiJi8RZrWp/F+qta1DeRrSChtqgUkMamj5d4vk6QQOSZnADOa8aopGwIu13QQiG4lV6Rla+OZkMT+O+keR0Qb9WxIQb9wLzdEmUU/DkW/0FO1zE8S78Z0pNMmU3quGgJRY1S+XoF4TiMQIk0dl+IRi9vlgKgFQR+qffOF/IAeedLHMPTFQP6t5ffGk9N5KWolhQkyEIfRtRtn7eSvQscufkn4vHuyOVwI34WLoii0hCHgcmA41qIkZhF0zGpHI82XUik59CZHugmpg0Oi5caofNN0QxOwPvqY0Ox17wvecbUYPvweBn40BqtGNfudmcYJBJ7wVnVj9k1kOt7y8kOYQRyd/kLgkT7TFVKVj43qnQ=[/tex]上式乘以 [tex=3.071x1.5]xIbhfnA4ko32sgGHET4h2Cg7ORVeaqW733f3JR7SEk4=[/tex], 得[tex=23.786x5.786]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[/tex]上式乘以[tex=1.571x1.429]8/hDdNovbYWxh1vnWYNqqkV2efYMj7xHBi/6+q8Fa6w=[/tex],得[tex=26.714x5.929]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[/tex]在MHA的通常浓度下[tex=1.214x1.357]sCR6ggRfj9KS+ynGZty9eGasaLnSINH7l/tLUAkrxOk=[/tex]值不是很小),[tex=5.857x1.5]fB/gCEGCPYstGCQ01oF4dtHIWTMpevuOvN6gPj/MdVh9xOPbkd6oLXoQ6oH9VcyM[/tex], 并且 [tex=13.357x1.429]8/hDdNovbYWxh1vnWYNqqoE5FqhRQcBTLjQ3TXCsAlCvOz/xRWuMJjXuUwgvP/TWzt5FScQl9haG6zodLV/2TPtpjF23bdMNmig76l96rcD/avDHxhgz6K8CLIl4C+t+K0qx11rNPHbQgUxNOrVSsw==[/tex], 所以上式近似表达为[tex=18.286x5.071]9XLejDX4y76F3QvbQn7xyQgVnDcazTCKb0ed+Y7YVCywCal3AxMWqDGnyUI1XhYIVbUg7Qz0FvLPKkCDASRGdctJgPyYrV3bhS3XeVm677cFVP0LqIuTNp6GAEHRVbUmQBl3CHt88SZc2LnQ5L5Lq2Jy9e4ljSUEs2IO30L7Q9CRIH0zgrQMaqGMEuVzHwGUZPqx3HEIyFNl7BZkDISg1wsJPvrrky7ERgj7sth/f2M99zCjQnk3gNls/TfXOz6aDqZZlbpo1RS9LEewXHevZiAvuP5AMnPwN3mqu9qZn0YtmOhM43yrOvD/DeRySt5zTQ30AFesRRaBuwK8lbeqL3xs6waSsY3QIg4Jevbd3GY=[/tex](6)式(6)即为[tex=5.143x1.429]HHWOyOFTLR84yHgjM+P7Tacuoy202SvFZoSBQ2MEX/H5yl3VQA7+2BKeoExSCu/h[/tex]时[tex=2.214x1.143]535iFBM5uLqt61Bvgn21oQ==[/tex]溶液中[tex=3.071x1.5]xIbhfnA4ko32sgGHET4h2Cg7ORVeaqW733f3JR7SEk4=[/tex]的近似计算式。从计算式可以 看出,通常浓度的酸式盐溶液[tex=3.071x1.5]xIbhfnA4ko32sgGHET4h2Cg7ORVeaqW733f3JR7SEk4=[/tex]与酸式盐的浓度无关,而只决定于酸式盐 其酸式根离子的解离常数与其前一级解离常数乘积的大小。

    内容

    • 0

      中国大学MOOC: 根据酸式盐 pH 计算的最简式,0.10 mol/L NaHCO3 溶液和 0.20 mol/L NaHCO3 溶液(H2CO3 的 pKa1 = 6.38,pKa2 = 10.25)的 pH 值近似相等。

    • 1

      酸式盐的pH值不一定大于7。

    • 2

      酸式盐溶液一定显酸性。

    • 3

      如何测定溶液的PH?

    • 4

      酸式盐的pH值不一定大于7。 A: 正确 B: 错误