Calculate pH of a buffer prepared by adding 10 mL of 0.10 M acetic acid to 20 mL of 0.1 M sodium acetate [pKa (CH3COOH) = 4.74]

Question

Calculate pH of a buffer prepared by adding 10 mL of 0.10 M acetic acid to 20 mL of 0.1 M sodium acetate [pKa (CH3COOH) = 4.74] (A) 3.00 (B) 4.44 (C) 4.74 (D) 5.04

Tardigrade Admin · Accepted Answer

[ CH 3 COOH ] = text millimoles of CH 3 COOH =0.1 × 10=1.0 [ CH 3 COONa ] = text millimoles of CH 3 COONa =0.1 × 20=2.0 From, Henderson Hasselbalch equation, pH = p Ka+ log ([ text conjugate base ]/[ text acid ]) =4.74+ log (2/1) =4.74+0.30=5.04

Q. Calculate $p H$ of a buffer prepared by adding $10 m L$ of $0.10 M$ acetic acid to $20 m L$ of $0.1 M$ sodium acetate [ $p K_{a} (C H_{3} COO H) = 4.74]$

3.00

4.44

4.74

5.04

$[C H_{3} COO H] = millimoles of C H_{3} COO H$
$= 0.1 \times 10 = 1.0$
$[C H_{3} COON a] = millimoles of C H_{3} COON a$
$= 0.1 \times 20 = 2.0$
From, Henderson Hasselbalch equation,
$p H = p K_{a} + lo g \frac{[ conjugate base ]}{[ acid ]}$
$= 4.74 + lo g \frac{2}{1}$
$= 4.74 + 0.30 = 5.04$

Q. Calculate pH of a buffer prepared by adding 10mL of 0.10M acetic acid to 20mL of 0.1M sodium acetate [pKa​(CH3​COOH)=4.74]