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Buffer Solution Question. HELP!! watch

1. Hi.

I attempted question 4b and obtained a pH change of 6.71. However, the answer states that there is a pH change of 0.02. I know I must have done something wrong because the pH is only affected ever so slightly.

Could someone attempt this question and explain how they obtained the answer.
Thanks!
2. So I said

old pH = pKa + log([A-]/[HA]) = pKa + log([CH3COONa]/[CH3COOH]) = 4.5834
new pH = pKa + log([A-]/[HA])) = pKa + log([CH3COONa + NaOH]/[CH3COOH-NaOH]) = 4.5979

so change in pH is 0.0144, however I feel that is far too small...
3. (Original post by Darth_Narwhale)
So I said

old pH = pKa + log([A-]/[HA]) = pKa + log([CH3COONa]/[CH3COOH]) = 4.5834
new pH = pKa + log([A-]/[HA])) = pKa + log([CH3COONa + NaOH]/[CH3COOH-NaOH]) = 4.5979

so change in pH is 0.0144, however I feel that is far too small...
The change in pH is 0.02. I'm not sure if you obtained that answer through rounding errors, but it seems close enough.

Also, I obtained the answer through a different method than yours.

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