Given the balanced ionic equation:
\[ 3\text{Pb}^{2+} + 2\text{Cr} \rightarrow 3\text{Pb} + 2\text{Cr}^{3+} \]
What is the number of moles of electrons gained by 3.0 moles of lead ions?
1. 5.0 mol
2. 2.0 mol
3. 3.0 mol
4. 6.0 mol
Answer (3)
answer: 6......................
Answer : The correct option is, (4) 6.0 mol
Explanation :
The given balanced ionic equation is,
3 P b 2 + + 2 C r → 3 P b + 2 C r 3 +
In this reaction , lead undergoes reduction and chromium undergoes oxidation.
Oxidation reaction : It is the reaction in which a substance looses its electrons. In this oxidation state increases.
Reduction reaction : It is the reaction in which a substance gains electrons. In this oxidation state decreases.
**Half reactions of oxidation and reduction are : **
Oxidation : 2 C r → 2 C r 3 + + 6 e −
Reduction : 3 P b 2 + + 6 e − → 3 P b
From the reduction reaction, we conclude that 6 moles of electrons gained by the 3 moles of lead ions.
Hence, the correct option is, (4) 6.0 mole
The number of moles of electrons gained by 3.0 moles of lead ions is 6.0 moles. This is determined by the reduction process where each lead ion gains 2 electrons. Therefore, the correct answer is option 4: 6.0 mol.
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