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常温下,0.001 mol/L盐酸的pH是多少?相信学过pH计算的学生能很快答出是3。可是又有多少人知道,常温下,0.001 mol/L盐酸的pH不是精确等于3,而是近似等于3。因为,在0.001 mol/L盐酸中,氢离子来源于氯化氢的电离和水的电离,而水的电离受制于氯化氢的电离,控制溶液氢离子浓度的是氯化氢的电离。显然,溶液中氢离子的浓度难以精确求算,因而溶液的pH也不可能精确计算。然而,常温下水电离出来的氢离子的浓度很小(为10~(-7)mol/L),受抑制后更小,此时我们采用模糊处理——忽略水的电离,这样对结果不会有大的影响,所以在忽略水的电离后0.001 mol/L盐酸的pH等于3。
At room temperature, what is the pH of 0.001 mol / L hydrochloric acid? But how many people know, at room temperature, 0.001 mol / L hydrochloric acid pH is not exactly equal to 3, but approximately equal to 3. Because in 0.001 mol / L hydrochloric acid, hydrogen ions are derived from the ionization of hydrogen chloride and water ionization, and the ionization of water is governed by the ionization of hydrogen chloride. The hydrogen ion concentration is controlled by the ionization of hydrogen chloride. Obviously, the concentration of hydrogen ions in the solution is difficult to calculate accurately, so the pH of the solution can not be accurately calculated. However, at room temperature, the concentration of hydrogen ionized by the water is very small (10 -7 mol / L) and is smaller after suppression. At this time, we adopt the blurring process - neglecting the ionization of water so that the result will not Has a large effect, so the pH of 0.001 mol / L hydrochloric acid equals 3 after ignoring the ionization of water.