What is the ph of a buffer in which the concentration of benzoic acid, c6h5cooh, is 0.040 m and the concentration of sodium benzoate, nac6h5coo, is 0.015 m ? ka of c6h5cooh is 6.30 x 10-5

pH=4.63

Explanation:

The firt step is identify the Acid and the conjugated base:

HA <=> +  

So, for this case we will have:

<=>   +  

Then:

HA =

=

With this in mind we can use the henderson-hasselbach equation:

pH = pKa + Log

We can calculate the pKa first

Then we can put the values in the equation:

pH = 4.2 + Log()

pH= 4.63