Question

20 mL solution is `0.1` M ferrous sulphate was completely oxidised using a suitable oxidising agent . What is the number of electrons exchanged ?
A. `1.204 xx 10^(22)`
B. `193`
C. `1930`
D. `1.204 xx 10^(21)`

Answer 1

Correct Answer - D
During oxidation of `FeSO_(4) , Fe^(2+)` ion is oxidises into `Fe^(3+)` ion.
`Fe^(2+) to Fe^(3+) + e^(-)`
i.e, `1e^(-)` is transferred from 1 molecule of `FeSO_(4)` , i.e, from 1 `Fe^(2+)` ion .
Now , molarity of `FeSO_(4)` solution = 0.1 M
and volume of solution = 20 mL = `(20)/(1000)` L
`therefore` Number of moles = `0.1 xx (20)/(1000) = 0.002`
`because` In 1 moles `FeSO_(4) ` , number of molecules = `6.022 xx 10^(23)`
`therefore` In 0.002 mol `FeSO_(4)` , number of molecules `= 6.022 xx 10^(23) xx 0.002 = 1.204 xx 10^(21)`
`therefore` Number of electrons transferred
`= 1.204 xx 10^(21)`