The number of Faraday.s (F) required to produce 20 g of calcium from `CaCl_(2)` (Atomic mass of Ca= 40 g `"mol"^(-1)` is:

Options

A. 2
B. 3
C. 4
D. 1

Answer

D

Explanation

1 equivalent of any substance is deposited by 1 F of charge.
We have, 20 g calcium
The balance reaction will The charge on Ca in `CaCl_(2)`
Cl , has -1 charge so that:
Ca + 2(-1) =0
Ca =2
We have as get 20 g Ca from `Ca^(2+)`
Number of required moles = mass / molar mass
Molar mass of Ca is 40g/mol and required mass of Ca is 20 g
Hence, number of moles = 20/40
= 0.5 mol
Electricity required to produce 1 mol of calcium = 2F
The electricity required to produce 0.5 mol of calcium
`=0.5 xx 2F`
= 1F