Question

Identify reductant in following reaction: $\text{C}_2\text{O}_4^{2-} + \text{MnO}_4^- + \text{H}^+ \longrightarrow \text{Mn}^{2+} + \text{CO}_2 + \text{H}_2\text{O}$

• A. $\text{H}^+$
• B. $\text{H}_2\text{O}$
• C. $\text{C}_2\text{O}_4^{2-}$
• D. $\text{MnO}_4^-$

Hint:

Look for the element that is gaining oxygen links or shedding electrons! Carbon moves from a crowded $+3$ oxalate state to a fully oxidized $+4$ dioxide state, signaling a classic oxidation process that defines a reducing agent.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The problem provides an unbalanced net ionic equation for a redox chemical process. We need to analyze the changes in oxidation states for the individual elements to identify the reductant (reducing agent).

Step 2: Key Formula or Approach:
By chemical definition:

• The

reductant is the species that undergoes oxidation (loses electrons), causing its oxidation number to increase.

• The

oxidant is the species that undergoes reduction (gains electrons), causing its oxidation number to decrease.


Step 3: Detailed Explanation:
Let's systematically compute and track the oxidation numbers for the key elements on both sides of the arrow:

• For Manganese in Permanganate ($\text{MnO}_4^-$): Let the oxidation number of Mn be $x$. Oxygen typically carries an oxidation state of $-2$: $$ x + 4(-2) = -1 \implies x - 8 = -1 \implies x = +7 $$ On the product side, Manganese transforms into the free monatomic ion $\text{Mn}^{2+}$, which has an oxidation number of $+2$. Since its value dropped from $+7 \rightarrow +2$, $\text{MnO}_4^-$ undergoes reduction and acts as the oxidant. ```

• For Carbon in Oxalate (\(\text{C}_2\text{O}_4^{2-}\)): Let the oxidation number of carbon be \(y\): \[ 2(y) + 4(-2) = -2 \implies 2y - 8 = -2 \implies 2y = +6 \implies y = +3 \] On the product side, Carbon is present in carbon dioxide (\(\text{CO}_2\)). Let its oxidation number there be \(z\): \[ z + 2(-2) = 0 \implies z - 4 = 0 \implies z = +4 \] Since the oxidation number of carbon increased from \(+3 \rightarrow +4\), it has lost electrons and undergone oxidation. ```
Because the oxalate ion ($\text{C}_2\text{O}_4^{2-}$) supplies the electrons that reduce manganese, it serves as the reductant.

Step 4: Final Answer: The reductant in the given redox pathway is $\text{C}_2\text{O}_4^{2-}$, which corresponds to option (C).