Calculate the pH of the following aqueous solutions prepared by adding 20.0 cm3 0.10M NH4Cl to 20.0 cm3 0.18M HCl.
The answer is 1.05
calculate ph
2009-08-06 4:40 am
回答 (1)
2009-08-06 8:37 am
✔ 最佳答案
Ionic product of water, Kw = 1 x 10-14 M2The dissociation constant of NH3, Kb = 1.8 x 10-5 M
NH4+(aq) ≒ NH3(aq) + H+(aq)
Kh = Kw/Kh = (1 x 10-14)/(1.8 x 10-5) = 5.56 x 10-10 M
At start (just after mixing):
[NH4+]o = 0.1 x [20/(20 + 20)] = 0.05 M
[H+]o = 0.18 x [20/(20 + 20)] = 0.09 M
At equilibrium:
Since Kh is very small,
[H+] ≈ [H+]o = 0.09 M
pH = -log[H+] = -log(0.09) = 1.05
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