A buffer contains 0.17 mol of propionic acid ( C2H5COOH ) and 0.14 mol of sodium propionate (C2H5COONa) in 1.20 L. What is the pH of the buffer after the addition of 0.01 mol of HI

The pH of the buffer after addition of given amount of HI is 4.76

Explanation:

We are given:

Initial moles of propionic acid = 0.17 moles

Initial moles of sodium propionate = 0.14 moles

Moles of HI added = 0.01 moles

The chemical equation for the reaction of HI and sodium propionate follows:

Initial:                      0.14            0.01         0.17

At eqllm:                 0.13               -            0.18

Total volume of the container = 1.20 L

To calculate the pH of acidic buffer, we use the equation given by Henderson Hasselbalch:

We are given:  

= negative logarithm of acid dissociation constant of propionic acid = 4.87

pH = ?

Putting values in above equation, we get:

Hence, the pH of the buffer after addition of given amount of HI is 4.76

thats how its supposed to be