Question

You need to produce a buffer solution that has a pH of 5.39. You already have a solution that contains 10. mmol (millimoles) of acetic acid. How many millimoles of acetate (the conjugate base of acetic acid) will you need to add to this solution?

Answer 1

Milli moles of acetate = 43.65 mmol

Step-by-step explanation:

The pH of a buffer solution is calculated using Henderson Hassalbalch's equation, which is:

`pH=pKa+log([salt])/([acid])`

Where

[Salt] = concentration of salt (sodium acetate, the conjugate base)

[acid] = concentration of acid (acetic acid) = 10 mmol

pH = 5.39

For acetic acid

pKa =4.75

Putting values

`5.39=4.75+log([acetate])/([10mmol])`

`0.64=log([acetate])/(10)`

Taking antilog

`4.365=([acetate])/(10)`

moles of acetate = 43.65 mmol