Answer:

Step-by-step explanation:
Hello,
In this case, for the calculation of the pH of the given buffer we need to use the Henderson-Hasselbach equation:
![pH=pKa+log(([base])/([acid]) )](https://img.qammunity.org/2021/formulas/chemistry/college/8dmrsjloj30y2yhkiycsj9lw9h9a6w3h5m.png)
Whereas the pKa for benzoic acid is 4.19, the concentration of the base is 0.15 M (sodium benzoate) and the concentration of the acid is 0.25 M (benzoic acid), therefore, the pH turns out:

Regards.