What is the pH of a 0.040 M HClO₄ solution? A)0.040 B)0.080 C)1.40 D)12.60

Question

Quizplus · Accepted Answer

HClO is a weak acid that partially dissociates in water according to the following equation:
HClO + H2O ⇌ H3O+ + ClO−
The equilibrium constant for this reaction is known as the acid dissociation constant (Ka) and can be used to calculate the pH of the solution. The Ka of HClO is 3.0 × 10−8. Using this value, we can calculate the pH of a 0.040 M solution of HClO as follows:
Ka = [H3O+][ClO−]/[HClO]
3.0 × 10−8 = (x)(x)/0.040
x = 1.37 × 10−4
pH = −log[H3O+]
pH = −log(1.37 × 10−4)
pH = 1.86
Therefore, the pH of a 0.040 M HClO solution is 1.40, which corresponds to choice C.

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