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JEE Main levelOne or more correct optionsDifficulty 2 of 3ie031

A weak monobasic acid HA is diluted with water at constant temperature. Which statements are correct?

AThe degree of ionisation $α$ increases.
BThe ionisation constant $K_{a}$ remains unchanged.
CThe concentration $[H X^{+}]$ increases.
DThe pH of the solution increases.

Answer: A, B, D

Dilution raises

α

(Ostwald:

α \approx K_{a} / c

) and

K_{a}

is temperature-dependent only. However

[H X^{+}] = c α \propto c

falls, so the pH rises. Options 1, 2 and 4 are correct.

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