Question

Choose the correct statement(s):
A) ${\text{1}}$ mole of $Mn{O_4}^ - $ ion can oxidise ${\text{5}}$ moles of $F{e^{2 + }}$ ion in acidic medium.
B) ${\text{1}}$ mole of $C{r_2}{O_7}^{2 - }$ ion can oxidise ${\text{6}}$ moles of $F{e^{2 + }}$ ions in acidic medium.
C) ${\text{1}}$ mole of $C{u_2}S$ can be oxidised by ${\text{1}} \cdot {\text{6}}$ moles of $Mn{O_4}^ - $ ions in acidic medium.
D) ${\text{1}}$ mole of $C{u_2}S$ can be oxidised by ${\text{1}} \cdot 33$ moles of $C{r_2}{O_7}^{2 - }$ ions in acidic medium.

Answer 1

Hint: Oxidation is the process where the gain of electrons happens. Analyze the given statements and the reaction where the oxidation process happens in an acidic medium and justify accordingly. This question may have multiple correct choices.

Complete step by step answer:
1) First of all let's analyze each given sentence one by one. In the first sentence reaction, one mole of permanganate ion can gain ${\text{5}}$ moles of electrons in an acidic medium, and in the case of ${\text{1}}$ mole of iron(II) ion, there is the loss of one mole of the electron. Therefore the statement ${\text{1}}$ mole of $Mn{O_4}^ - $ ion can oxidise ${\text{5}}$ moles of $F{e^{2 + }}$ ion in acidic medium is the correct choice.
2) In the second statement one mole of dichromate ion can gain ${\text{6}}$ moles of electrons and in the case of one mole of iron(II) ion, there is a loss of one mole of electrons. Therefore, the statement ${\text{1}}$ mole of $C{r_2}{O_7}^{2 - }$ ion can oxidise ${\text{6}}$ moles of $F{e^{2 + }}$ ions in acidic medium is also a correct choice.
3) In the third statement while performing the reaction in an acidic medium there is one mole of permanganate ion which gains ${\text{5}}$ moles of electrons and in the case of ${\text{1}}$ mole of $C{u_2}S$ there is the loss of two moles of electrons. Therefore, the statement ${\text{1}}$ mole of $C{u_2}S$ is oxidised by ${\text{1}} \cdot {\text{6}}$ moles of $Mn{O_4}^ - $ ions in acidic medium is an incorrect statement.
4) In the fourth statement one mole of dichromate ion will gains ${\text{6}}$ moles of electrons in an acidic medium and in the case of one mole of $C{u_2}S$ there is a loss of two moles of electrons. Therefore, the statement ${\text{1}}$ mole of $C{u_2}S$ can be oxidised by ${\text{1}} \cdot 33$ moles of $C{r_2}{O_7}^{2 - }$ ions in acidic medium is an incorrect statement.

Therefore, after analyzing all the statements the statements in options A and B are the correct choice of answer.

Note:
In an acidic medium there is the gain of electrons by the negatively charged molecules and the charge will convert into a positive charge from the negative charge as the oxidation process is the gain of electrons. The number of differences in the oxidation state between the initial and final is the number of moles required.