Question

How many grams of cobalt metal will be deposited when a solution of cobalt (II) chloride is electrolyzed with a current of 10 amperes for 109 minutes (1 Faraday = 96,500 C; Atomic mass of Co = 59 u) :

• A. 4
• B. 20
• C. 40
• D. 0.66

Answer 1

The Correct Option is B

To determine how many grams of cobalt metal are deposited during the electrolysis of cobalt (II) chloride with a current of 10 amperes for 109 minutes, we can use Faraday's laws of electrolysis. Let's go through the steps step-by-step.

1. Calculate the total charge passed through the solution:
   • Current, I = 10 \, \text{A}
   • Time, t = 109 \, \text{minutes} = 109 \times 60 \, \text{seconds} = 6540 \, \text{seconds}
   • Total charge, Q = I \times t = 10 \times 6540 = 65400 \, \text{coulombs}
2. Determine the moles of electrons transferred:
   • Using Faraday's constant, 1 \, \text{Faraday} = 96500 \, \text{coulombs}
   • Moles of electrons, \frac{65400}{96500} = 0.6771 \, \text{moles of electrons}
3. Calculate the moles of cobalt deposited:
   • The reaction for cobalt deposition is: \text{Co}^{2+} + 2e^- \rightarrow \text{Co}
   • This implies 2 moles of electrons are needed to deposit 1 mole of cobalt.
   • Moles of cobalt deposited: \frac{0.6771}{2} = 0.3386 \, \text{moles}
4. Calculate the mass of cobalt deposited:
   • Atomic mass of cobalt, 59 \, \text{u}
   • Mass deposited, 0.3386 \times 59 = 19.9954 \approx 20 \, \text{grams}

Hence, 20 grams of cobalt metal will be deposited, which confirms the correct option as 20.