You are asked to prepare a ph = 4.00 buffer starting from 1.50 l of 0.0200 m solution of benzoic acid (c6h5cooh and some added sodium benzoate salt (c6h5coona. a find the ph of the benzoic acid solution before adding the salt. b use the henderson-hasselbalck equation to derive how many moles of the salt you should add. c how many grams of the salt should you add?

Question

Chemistry

Nigel Dominguez

21 July, 01:03

You are asked to prepare a ph = 4.00 buffer starting from 1.50 l of 0.0200 m solution of benzoic acid (c6h5cooh and some added sodium benzoate salt (c6h5coona. a find the ph of the benzoic acid solution before adding the salt. b use the henderson-hasselbalck equation to derive how many moles of the salt you should add. c how many grams of the salt should you add?

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Kaiden Bryant · Answer 1

The henderson-hasselbalck equation is this

pH = pK + log [salt]/[acid]

We are given with

pH = 4.00

1.50 l of 0.0200 m solution of benzoic acid

The pK for benzoic acid is

4.20

Solving for the moles of salt,

4 = 4.2 + log 1.5 (0.02) / n

n = 71.62 moles

The mass is

m = 71.62 (249.2)

m = 17800 grams