Q19 / 150 · MHT CET 2026 (13 April Shift 1) · Chemistry
A weak monobasic acid is 0.04 % dissociated in 0.25 M solution. What is pH of the solution?
- A$2.5$
- Correct answerB$4$
- C$5$
- D$10$
Solution
Given concentration of the weak monobasic acid, $C = 0.25$ M.
Degree of dissociation, $\alpha = 0.04\% = \dfrac{0.04}{100} = 4 \times 10^{-4}$.
For a weak monobasic acid, the hydrogen ion concentration is given by:
$[H^+] = C\alpha$
Substituting the values:
$[H^+] = 0.25 \times 4 \times 10^{-4} = 10^{-4}$ M.
The pH of the solution is:
$pH = -\log[H^+]$
$pH = -\log(10^{-4}) = 4$.
Answer: $4$
Degree of dissociation, $\alpha = 0.04\% = \dfrac{0.04}{100} = 4 \times 10^{-4}$.
For a weak monobasic acid, the hydrogen ion concentration is given by:
$[H^+] = C\alpha$
Substituting the values:
$[H^+] = 0.25 \times 4 \times 10^{-4} = 10^{-4}$ M.
The pH of the solution is:
$pH = -\log[H^+]$
$pH = -\log(10^{-4}) = 4$.
Answer: $4$
Hence, the correct answer is option: 'B'.