Question

A current of $1.40$ ampere is passed through $500 \,mL$ of $0.180 \,M$ solution of zinc sulphate for $200$ seconds. What will be the molarity of $Zn^{2+}$ ions after deposition of zinc?

• A. $0.154\, M$
• B. $0.177\, M$
• C. $2\,M$
• D. $0.180 \,M$

Answer 1

Answer: (B)

Amount of charge passed $= 1.40 \times 200$
$= 280$ Coulombs
No. of moles of $Zn$ deposited by passing $280\, C$ of charge
$=\frac{1}{2\times96500}\times280=0.00145$
Molarity of zinc after deposition of zinc
$=0.180-\frac{0.00145\times1000}{500}$
$=0.180-0.0029$
$=0.177\,M$