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a chemistry pH qs - adding strong acid to buffer solution?
A 1.00 L aqueous solution contains 0.0550 moles of acetic acid (CH3COOH) and 0.0350 moles of sodium acetate CH3COONa. What is the pH of the solution when 0.0050 moles of HCl are added without change in volume?
[pKb (CH3COO-) = 9.3]
my teacher did a similar qs like this in the class but with the addition of NaOH. please give me a detailed and, i am really struggling with this qs.
Thanks for your help,
Cheers,
2 Answers
- Simonizer1218Lv 77 years ago
Recognize that when HCl is added, it will react with the sodium acetate, CH3COONa to form acetic acid, CH3COOH. So, the [CH3COOH] will increase, and the [CH3COONa] will decrease by the same amount.
Initial [CH3COOH] = 0.0550
Initial [CH3COONa] = 0.0350
Final [CH3COOH] = 0.0550 + 0.005 = 0.06
Final [CH3COONa] = 0.0350 - 0.005 = 0.030
pKa = 14 - 9.3 = 4.7
pH = pKa + log [CH3COONa]/[CH3COOH] <--- Henderson Hasselbalch
pH = 4.7 + log 0.03/0.06
pH = 4.7 + (-0.3)
pH = 4.4
