Calculate the pH of a solution that is 0.239 M acetic acid and 0.190 M sodium acetate. The Ka of acetic acid is 1.76×10–5 at 25°C. What is the pH of this mixture at 0°C? (At 0°C, Ka = 1.64x10-5)

Respuesta :

Answer: The pH of the mixture at 0°C is 4.68

Explanation:

To calculate the pH at 0°C, we use the equation given by Henderson Hasselbalch:

[tex]pH=pK_a+\log(\frac{[salt]}{[acid]})[/tex]

[tex]pH=pK_a+\log(\frac{[CH_3COONa]}{[CH_3COOH]})[/tex]

We are given:

[tex]pK_a[/tex] = negative logarithm of acid dissociation constant of acetic acid at 0°C = 4.78

[tex][CH_3COONa]=0.190M[/tex]

[tex][CH_3COOH]=0.239M[/tex]

pH = ?

Putting values in above equation, we get:

[tex]pH=4.78+\log(\frac{0.190}{0.239})\\\\pH=4.68[/tex]

Hence, the pH of the mixture at 0°C is 4.68