Question

The approximate time duration in hours to electroplate 30 g of calcium from molten calcium chloride using a current of 5 amp is :
[Atomic mass of $Ca=40$]

• A. 8
• B. 80
• C. 10
• D. 16

Answer 1

The correct option is A 8

30 g of $Ca$ (atomic weight 40 g/mol) corresponds to $\frac{30}{40}=0.75$ moles.

1 mole of $Ca$ corresponds to 2 moles of electrons. 0.75 moles of $Ca$ will correspond to $2\times 0.75=1.5$ moles of electron.

1 mole of electron corresponds to $96500$ coulombs of electricity. 1.5 moles of electrons will correspond to $96500\times 1.5=144750$ coloumbs of electricity.

The current is 5 amp.
The time required to electroplate calcium is $=\frac{Q}{i}=\frac{144750}{5}=28950$ seconds. Convert the unit of time from seconds to hours.

Time $=\frac{28950}{3600}=8$ hours.