chemical equilibrium
2008-06-23 12:04 am
1 dm^3 of a solution is obtained by mixing 500cm^3 of 0.200 M HCl and 500cm^3 of 0.700M NaCN. Given that the dissociation constant of HCN is 4.0X10^-10 mol dm^-3, calculate the pH of the solution.
回答 (1)
2008-06-23 7:58 am
✔ 最佳答案
H+(aq) reacts with CN-(aq) to give HCN(aq):H+(aq) + CN-(aq) → HCN(aq)
[HCN] = 0.2 x (500/1000) = 0.1 M
[CN-] = [0.7 x (500/1000)] - [0.2 x (500/1000)] = 0.25 M
Consider the following equilibrium:
HCN(aq) + H2O(l) ≒ CN-(aq) + H3O+(aq)
pH = pH - log([HCN]/[CN-])
pH = -log(4 x 10-10) -log(0.1/0.25)
pH = 9.8
2008-06-22 23:59:49 補充：
The solution is alkaline. This is because HCN is a very weak acid, and the conjugate base CN^- is thus rather basic.
收錄日期: 2021-04-23 23:05:54
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080622000051KK01497