1. Tardigrade
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  3. Chemistry
  4. 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]

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Q. 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 [$pK_a (CH_3COOH) = 4.74]$

VITEEEVITEEE 2013

Solution:

$\left[ CH _{3} COOH \right] =\text { millimoles of } CH _{3} COOH $
$=0.1 \times 10=1.0$
$\left[ CH _{3} COONa \right] =\text { millimoles of } CH _{3} COONa $
$=0.1 \times 20=2.0$
From, Henderson Hasselbalch equation,
$pH = p K_{a}+\log \frac{[\text { conjugate base }]}{[\text { acid }]}$
$=4.74+\log \frac{2}{1}$
$=4.74+0.30=5.04$