The answer is 8.63, please show your solution steps by steps, thank you so much!!
更新1:
what about if it is a buffer solution??
calculate pH
2009-08-06 7:41 pm
Calculate the pH of the aqueous solutions prepared by adding 20cm3 of 1.12M HCl to 10cm3 of 0.16M CH3COOH + 20cm3 of 0.20 M KOH.
The answer is 8.63, please show your solution steps by steps, thank you so much!!
The answer is 8.63, please show your solution steps by steps, thank you so much!!
回答 (2)
2009-08-07 1:42 am
✔ 最佳答案
The given answer (8.63) is incorrect. Please check your question.The HCl used is much concentrated than the KOH. Therefore, the final solution must be very acidic and the pH should be much less than 7.
No. of moles of H+ added = 1.12 x (20/1000) = 0.0224 mol
No. of moles of CH3COOH added = 0.16 x (10/1000) = 0.0016 mol
No. of moles of OH- added = 0.2 x (20/1000) = 0.004 mol
Volume of the solution = (20 + 10 + 20) cm3 = 50 cm3 = 0.05 dm3
All the OH- reacts with part of H+ to form H2O.
[H+]o = (0.0224 - 0.004)/0.05 = 0.368 M
[CH3COOH]o = 0.0016/0.05 = 0.032 M
Consider the dissociation of CH3COOH in the solution.
CH3COOH(aq) = CH3COO-(aq) + H+(aq)
Because Ka = 1.8 x 10-5 M is very small and the common ion effect due to H+, the above dissociation is to an extremely extent.
At equilibrium:
[H+] = [H+]o + (M of H+ due to dissociation) ≈ [H+]o ≈ 0.368
pH = -log(0.368) = 0.43
2009-08-06 10:59 pm
Pls. check the Q
Since 20 cm^3 of 1.12M HCl is in excess when mixing with 20 cm^3 of 0.20 M KOH, the resulting solution must be acidic after adding ethanoic acid.
Since 20 cm^3 of 1.12M HCl is in excess when mixing with 20 cm^3 of 0.20 M KOH, the resulting solution must be acidic after adding ethanoic acid.
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