50 mL of 0.1 M of H 3 CCOOH is titrated against 0.1 M NaOH solution. What will be the pH of the solution when 25 mL of NaOH is added? [Given: K a of H 3 C − COOH = 2 × 1 0 − 5 ; lo g 2 = 0.3 ]

Question

50 mL of 0.1 M of H 3 ​ CCOOH is titrated against 0.1 M NaOH solution. What will be the pH of the solution when 25 mL of NaOH is added? [Given: K a ​ of H 3 ​ C − COOH = 2 × 1 0 − 5 ; lo g 2 = 0.3 ]

TestHub · Accepted Answer

CH₃COOH + NaOH ⎯→ CH₃COONa + H₂O

Millimoles $t = 0$ : 5 2.5 0 0

Millimoles $t = t^{'}$ : 2.5 0 2.5

Here, the millimoles of CH₃COOH and CH₃COONa are the same. Together, they constitute an acidic buffer. For an acidic buffer:

$p H = p K_{a} + lo g \frac{[ s a lt ]}{[ a c i d ]}$

Because $[s a lt] = [a c i d]$ , So

$p H = p K_{a}$

$p H = - lo g (2 \times 1 0^{- 5})$

$p H = 4.7$

Chemistry - Ionic Equilibrium Question with Solution | TestHub

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