Question

On heating with concentrated $NaOH$ solution in an inert atmosphere of $C{O}_2$, white phosphorus gives a gas. Which of the following statements is incorrect about the gas?

Answer 1

$\text{Reaction of white phosphorous with sodium hydroxide}$

• As per the given question, the balanced chemical reaction is:

$P_4+3NaOH+3H_{2}O\to P{H}_3+3Na{H}_{2}P{O}_2$

When white phosphorus $\left(P_4\right)$ reacts with sodium hydroxide, sodium hypophosphite is produced along with the evolution of phosphine $\left(P{H}_3\right)$ gas.

The properties of $P{H}_3$ gas are as follows:

• It is the hydride of phosphorus.
• It is less basic than $N{H}_3$ (hydride of $N$) because on moving down the group, the size of the central atom increases. So, electron density on the central atom decreases and hence, its ability to donate pair of electrons decreases.
• It is a colourless gas which smells like rotten fish.

The solution of $P{H}_3$ in water decomposes in presence of light giving red phosphorus and $H_2$ gas.

$2P{H}_3\to 2P+3H_2$
(Red phosphorous)

Thus, the incorrect statement regarding $P{H}_3$ is that it is more basic than $N{H}_3$.

So, option $\left(C\right)$ is the correct answer.