Question

Be sure to answer all parts. What is the [H3O+] and the pH of a benzoic acid-benzoate buffer that consists of 0.22 M C6H5COOH and 0.41 M C6H5COONa? (Ka of benzoic acid = 6.3 × 10−5) Be sure to report your answer to the correct number of significant figures.

Answer 1

The pH will be 4.5

Step-by-step explanation:

The mixture of benzoic acid (weak acid) and its salt will make a buffer.

The pH of buffer solution can be calculated using Henderson Hassalbalch's equation, which is

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

pKa = -logKa

pKa = -log(
`6.3X10^(-5)`)

pKa = 4.2

`pH=4.2 + log(0.41)/(0.22)=4.2+0.27=4.47=4.5`