Question

What will be the volume of gases formed at anode at STP by electrolysis of above solution after passing 20 amp current for 28950 sec.? (Assume current efficiency to be 100% and one mole of gas occupies 22.4 L volume at STP).

• A. 44.8 L Br${}_2$
• B. 22.4 L Br${}_2$
• C. 22.4 L Cl${}_2$
• D. 44.8 L Cl${}_2$

Answer 1

Answer: (A), (C)

44.8 L Br${}_2$
22.4 L Cl${}_2$

Moles of electrons actually passed $=\frac{I\left(A\right)\times t\left(s\right)}{96500}=\frac{20\times 28950}{96500}=6$ mole electrons.

Among chloride and bromide ions, the bromide ion has lower discharge potential and is discharged first.

2L of 2M bromide ion solution contains 4 moles of bromide ions which will give 4 moles of electrons and form 2 moles of bromine.

Remaining 2 moles of electrons will be supplied by 2 moles of chloride ions to form 1 mole of chlorine.

Thus at anode, 44.8 L of bromine and 22.4 L of chlorine will be liberated.