Answer to Question #224839 in Biochemistry for SIYABONGA

Question

What is the pH of a mixture of 5 ml of 0.1 mol/litre sodium acetate and 4 ml of 0.1 mol/litre acetic acid? (pKa of acetic acid at 25oC = 4.76)

Answer 1

pK_a=4.76

K_a=1.74*10^-5

$Ka = \frac {[H^+] [CH_3COO^-]} {CH_3COOH]}$

$[H^+] = \frac {1.74 × 10^ {-5} × 0.0005}{0.0004} = 2.175 × 10^ {-5}$

$pH=-log_{10}(2.175×10^{-5})=4.66$