Identification of Gas W and Oxide X in Phosphorus Reaction

To determine the identity of the gas $\mathbf{W}$ and the oxide $\mathbf{X}$, we analyze the chemical reactions step-by-step:

1. Formation of Gas $\mathbf{W}$: When potassium chlorate ($\text{KClO}_3$) is thermally decomposed in the presence of manganese dioxide ($\text{MnO}_2$) as a catalyst, oxygen gas ($\text{O}_2$) is liberated along with potassium chloride: $2\text{KClO}_3(s) \xrightarrow[\Delta]{\text{MnO}_2} 2\text{KCl}(s) + 3\text{O}_2(g)$ Thus, the gas $\mathbf{W}$ is dioxygen, $\mathbf{O_2}$.

2. Formation of Oxide $\mathbf{X}$: White phosphorus ($\text{P}_4$) reacts with an excess amount of oxygen gas ($\mathbf{W}$) to form tetraphosphorus decoxide ($\text{P}_4\text{O}_{10}$): $\text{P}_4(s) + 5\text{O}_2(g) \text{ (excess)} \longrightarrow \text{P}_4\text{O}_{10}(s)$ Thus, the oxide $\mathbf{X}$ is $\mathbf{P_4O_{10}}$.

Therefore, $\mathbf{W}$ and $\mathbf{X}$ are $\text{O}_2$ and $\text{P}_4\text{O}_{10}$, respectively.

Correct Option: C ($\text{O}_2$ and $\text{P}_4\text{O}_{10}$)