NEET 2022 — Chemistry solution

NEET2022Chemistry

The pH of the solution containing 50 mL each of 0.10 M sodium acetate and 0.01 M acetic acid is [Given pK $_{a}$ of CH $_{3}$ COOH = 4.57]

Solution

A mixture of CH $_{3}$ COONa (salt of weak acid with strong base) and CH $_{3}$ COOH (weak acid) is an acidic buffer.

Henderson-Hasselbalch equation: $pH = p K_{a} + lo g \frac{[ Salt ]}{[ Acid ]}$ .

Since equal volumes are mixed, the ratio of moles equals the ratio of initial concentrations: $\frac{[ Salt ]}{[ Acid ]} = \frac{0.10}{0.01} = 10$ .

$pH = 4.57 + lo g 10 = 4.57 + 1 = 5.57$ .

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