Question

A 100.0mL dilute solution of Ag⁺ is electrolysed for 15.0 minutes with a current of 1.25mA and the silver is removed completely. What was the initial [Ag⁺]?

• A. \(2.32\times10^{-1}\)
• B. \(2.32\times10^{-4}\)
• C. \(2.32\times10^{-5}\)
• D. 1.16×10⁻5

Hint:

In electrolysis, moles of ions discharged are obtained directly from charge passed.

Answer 1

The Correct Option is B

Step 1: Charge passed: Q = It = 1.25×10⁻3×(15×60)=1.125C
Step 2: Moles of electrons: n = (Q)/(F)=(1.125)/(96500)=1.165×10⁻5
Step 3: For Ag⁺ + e⁻ → Ag, moles of Ag⁺ = moles of electrons.
Step 4: [Ag⁺] = frac1.165×10⁻50.1 =1.165×10⁻4≈2.32×10⁻4