Answer: 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:
[tex]C_2H_5COONa+HI\rightleftharpoons C_2H_5COOH+NaI[/tex]
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:
[tex]pH=pK_a+\log(\frac{[salt]}{[acid]})[/tex]
[tex]pH=pK_a+\log(\frac{[C_2H_5COONa]}{[C_2H_5COOH]})[/tex]
We are given:
[tex]pK_a[/tex] = negative logarithm of acid dissociation constant of propionic acid = 4.87
[tex][C_2H_5COONa]=\frac{0.14}{1.20}[/tex]
[tex][C_2H_5COOH]=\frac{0.18}{1.20}[/tex]
pH = ?
Putting values in above equation, we get:
[tex]pH=4.87+\log(\frac{0.14/1.20}{0.18/1.20})\\\\pH=4.76[/tex]
Hence, the pH of the buffer after addition of given amount of HI is 4.76
