Which from following statements is NOT true about isotopes?

$$ \text { Identify the product in the following reaction. } $$

A monobasic weak acid dissociates to $1.2 \%$ in its 0.01 M solution at 298 K . Calculate dissociation constant of it.

The solubility of calcium carbonate at 298 K is $6.4 \times 10^{-5} \mathrm{~mol} \mathrm{dm}^{-3}$. Calculate the value of solubility product at the same temperature?