Question

A 1 liter solution contains 0.382 M acetic acid and 0.287 M sodium acetate.

Addition of 0.315 moles of hydrochloric acid will:
(Assume that the volume does not change upon the addition of hydrochloric acid.)

Raise the pH slightly

Lower the pH slightly

Raise the pH by several units

Lower the pH by several units

Not change the pH

Exceed the buffer capacity

Answer 1

Given that

A 1 liter solution contains 0.382 M acetic acid and 0.287 M sodium acetate.

[acetic acid] = molarity x volume in Litres = 0.382 M x 1 L = 0.382 mol

[sodium acetate] = molarity x volume in Litres = 0.287 M x 1 L = 0.287 mol

Given that 0.315 moles of hydrochloric acid was added.

CH3COONa + HCl ---------> CH3COOH + NaCl

0.287 mol 0.315 mol

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It leads to formation of additional amount of acetic acid.

pH = pKa + log [sodium acetate ]/[acetic acid]

Therefore, it will lowers the pH slightly.

Ans: Lower the pH slightly