Question

The ratio of weights of hydrogen and magnessium deposited by the same amount of electricity from aqueous H2SO4 and fused MgSO4 are:​

Answer 1

The mass of Hydrogen : the mass of Magnesium = 2:1

Since 2 atoms of Hydrogen combines with $SO_{4}$ group while only 1 atom of Magnesium combines with $SO_{4}$ group.

Answer 2

The ratio of weight of hydrogen and magnessium:

Faraday's second equation states that the ratio of the weight of two compounds deposited by passing electricity through a solution is directly proportional to their equivalent weight.

In both $M g S O_{4}$  and  $H_{2} S O_{4}$ the equivalent weight is equal to molecular weight/2. Since the valency is equal to zero. So the equivalent weight of $M g S O_{4}$  is  $\frac{120}{2} = 60$. The equivalent weight of $H_{2} S O_{4}$  is equal to  $\frac{98}{2}=49$. Therefore the ratio weight of hydrogen and magnesium deposited is equal to $\frac{49}{60}$