Question

Difficulty: EasyFaraday's Laws of Electrolysis and Quantitative Calculations

Calculate the quantity of electricity, in Coulombs, required to deposit 0.108 g0.108\text{ g} of silver at the cathode during the electrolysis of silver trioxonitrate(V) solution. (Ag=108 g/mol\text{Ag} = 108\text{ g/mol}, 1 F=96,500 C/mol1\text{ F} = 96,500\text{ C/mol})

Answer: 96.5 C

Answer

The quantity of electricity required is 96.5 C96.5\text{ C}.
Depositing 0.108 g0.108\text{ g} of silver (molar mass 108 g/mol108\text{ g/mol}) requires 0.001 moles0.001\text{ moles} of silver atoms. According to the cathodic reaction Ag++eAg\text{Ag}^+ + \text{e}^- \rightarrow \text{Ag}, 1 mole1\text{ mole} of electrons (96,500 C96,500\text{ C}) is required to deposit 1 mole1\text{ mole} of Ag\text{Ag}. Therefore, the total charge required is 0.001×96,500 C=96.5 C0.001 \times 96,500\text{ C} = 96.5\text{ C}.

Step-by-Step Solution

1
Calculate the number of moles of silver deposited
Moles of Ag=0.108 g108 g/mol=0.001 mol\text{Moles of Ag} = \frac{0.108\text{ g}}{108\text{ g/mol}} = 0.001\text{ mol}
Number of moles is calculated by dividing mass by molar mass.
2
Determine the quantity of electricity (charge) required
Q=0.001 mol×96,500 C/mol=96.5 CQ = 0.001\text{ mol} \times 96,500\text{ C/mol} = 96.5\text{ C}
The reduction reaction Ag++eAg\text{Ag}^+ + \text{e}^- \rightarrow \text{Ag} shows 1 mole1\text{ mole} of electrons (1 F=96,500 C1\text{ F} = 96,500\text{ C}) deposits 1 mole1\text{ mole} of silver.

Key Concept

Faraday's First Law of Electrolysis and Quantitative Mass-Charge Relationship
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