Q. Consider the following redox reactions given below:
I. $NH_{4}NO_{3}\overset{\Delta }{ \rightarrow } \, N_{2}O+2H_{2}O$
II. $NH_{4}NO_{2}\overset{\Delta }{ \rightarrow }N_{2}+2H_{2}O$
III. $PCl_{5}\overset{\Delta }{ \rightarrow } \, PCl_{3}+Cl_{2}$
Which of the above is/are not disproportionation reaction?

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A

I and II

B

II and III

C

I and III

D

I, II and III

Solution:

I. $\text{NH}_{4}^{+} & \text{NO}_{3}^{-} & \rightarrow & \text{N}_{2}\text{O} & + & 2\text{H}_{2}\text{O} \\ -3 & +5 & & +1 & & $
It is a redox reaction but not a disproportionation reaction. Since, different N-species are involved.
II. $\text{NH}_{4}^{+} & + & \text{NO}_{2}^{-} & \rightarrow & \text{N}_{2} \\ -3 & & +3 & & 0$
Same as (I)
III. $\text{PCl}_{5} & \rightarrow & \text{PCl}_{3} & + & \text{Cl}_{2} \\ +5-1 & & +3-1 & & 0$
Thus, it is also not a disproportionation reaction.

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