Which of the following is not a disproportionation reaction? o I. NH NO N O 2H O II.P 3NaOH 3H O P H — Redox Reactions and Volumetric Analysis Chemistry Question

💡 Solution & Explanation

# Solution: Identifying Non-Disproportionation Reactions A **disproportionation reaction** occurs when a single element in one oxidation state is simultaneously oxidized AND reduced to form two different products. ## Analysis of Each Reaction: **I. $2NH_4NO_2 \rightarrow N_2 + 2H_2O$** - N in $NH_4^+$: oxidation state = -3 - N in $NO_2^-$: oxidation state = +3 - Products: N in $N_2$ = 0 - Conclusion: **Disproportionation** ✓ (N goes from -3 and +3 both → 0) **II. $P_4 + 3NaOH + 3H_2O \rightarrow PH_3 + 3NaH_2PO_2$** - P in $P_4$: oxidation state = 0 - Products: P in $PH_3$ = -3 and P in $NaH_2PO_2$ = +1 - Conclusion: **Disproportionation** ✓ (P goes from 0 → both -3 and +1) **III. $PCl_5 \rightarrow PCl_3 + Cl_2$** - P remains: +5 → +3 (reduction only) - Cl remains: -1 → 0 (oxidation only) - **Different elements change oxidation state** — this is a **decomposition reaction, NOT disproportionation** ✗ **IV. $IO^- + I^- + H^+ \rightarrow I_2 + H_2O$** - I in $IO^-$: +1; I in $I^-$: -1; I in $I_2$: 0 - Conclusion: **Disproportionation** ✓ (I goes from both +1 and -1 → 0) ## Answer: **B (III)** is NOT a disproport