Question

Phosphorous acid on heating gives the following products:
4$H_{3}P{O}_5\stackrel{\Delta }{\to }$ 3$H_{3}P{O}_4$+ $P{H}_3$
The above reaction is an example of:

• A. oxidation
• B. thermal decomposition
• C. disproportionation
• D. reduction

Answer 1

Answer: (C)

disproportionation

$4H_{3}P{O}_3\stackrel{\Delta }{⟶}3H_{3}P{O}_4+P{H}_3$
It is disproportional where Phosphorus changes from $+3$ to $-3$ and $+5$. So, this is an example of disproportion reaction.