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MHTCET 13 Apr 2026 Shift 1 Paper

Question : 59 of 150

Marks: +1, -0

A weak monobasic acid is 0.04 \% dissociated in 0.25 M solution. What is pH of the solution?

Solution:

Concept:

For a weak monobasic acid, the hydrogen ion concentration depends on its concentration and degree of dissociation.

Explanation:

Given concentration is

C = 0.25\ \mathrm{M}

The acid is

0.04\%

dissociated, so

\alpha = \frac{0.04}{100} = 0.0004

For a monobasic acid,

[\mathrm{H}^+] = C\alpha

Substituting the values,

[\mathrm{H}^+] = 0.25 \times 0.0004 = 0.0001\ \mathrm{M}

Thus,

[\mathrm{H}^+] = 10^{-4}\ \mathrm{M}

Now,

\mathrm{pH} = -\log[\mathrm{H}^+] = -\log(10^{-4}) = 4

Answer:

The pH of the solution is

4

Correct option: B.

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