Identification of Products Y and Z from Oxide Reaction

To determine the chemical identities of $\mathbf{Y}$ and $\mathbf{Z}$, we systematically trace the reaction sequence starting from the given passage:

1. Formation of Gas $\mathbf{W}$: When potassium chlorate ($\text{KClO}_3$) is heated in the presence of manganese dioxide ($\text{MnO}_2$) as a catalyst, it undergoes thermal decomposition to release oxygen gas ($\text{O}_2$): $2\text{KClO}_3 \xrightarrow[\Delta]{\text{MnO}_2} 2\text{KCl} + 3\text{O}_2\uparrow$ Hence, the gas $\mathbf{W}$ is oxygen ($\text{O}_2$).

2. Formation of Compound $\mathbf{X}$: When white phosphorus ($\text{P}_4$) reacts with an excess of oxygen gas ($\mathbf{W}$), phosphorus pentoxide ($\text{P}_4\text{O}_{10}$) is formed: $\text{P}_4 + 5\text{O}_2 (\text{excess}) \longrightarrow \text{P}_4\text{O}_{10}$ Hence, compound $\mathbf{X}$ is $\text{P}_4\text{O}_{10}$.

3. Formation of Products $\mathbf{Y}$ and $\mathbf{Z}$: Phosphorus pentoxide ($\text{P}_4\text{O}_{10}$) acts as a powerful dehydrating agent. When it reacts with pure (concentrated) nitric acid ($\text{HNO}_3$), it dehydrates $\text{HNO}_3$ to yield dinitrogen pentoxide ($\text{N}_2\text{O}_5$) while itself being converted to metaphosphoric acid ($\text{HPO}_3$): $4\text{HNO}_3 + \text{P}_4\text{O}_{10} \longrightarrow 2\text{N}_2\text{O}_5 + 4\text{HPO}_3$

Therefore, products $\mathbf{Y}$ and $\mathbf{Z}$ are $\text{N}_2\text{O}_5$ and $\text{HPO}_3$, respectively.

Correct Option: B