Question

please answer this question ​

Answer 1

0.5 g = 0.5 mol of (atomic, not molecular) hydrogen, so 0.5 mol of electrons was absorbed by the hydrogen.

In CuSO₄, copper is in a +2 oxidation state, so it takes 2 mol of electrons per 1 mol Cu to liberate it. Only 0.5 mol of electrons is provided, which is 0.25 of 2 mol, so it would be able to liberate only 0.5/2 = 0.25 mol Cu.

Now look up the molar mass of copper and multiply.