Question 6

1. Identification of $\mathbf{X}$: The reaction of $MnO_2$ with concentrated $HCl$ produces chlorine gas, which is greenish-yellow.

$MnO_2 + 4HCl \rightarrow MnCl_2 + Cl_2 + 2H_2O$. Thus, $\mathbf{X} = Cl_2$.

2. Identification of $\mathbf{Y}$: Reaction of excess chlorine with ammonia yields nitrogen trichloride. $NH_3 + 3Cl_2 (excess) \rightarrow NCl_3 + 3HCl$. Thus, $\mathbf{Y} = NCl_3$.
3. Identification of $\mathbf{Z}$: Reaction of chlorine with excess fluorine at $573\text{ K}$ yields chlorine trifluoride. $Cl_2 + 3F_2 (excess) \rightarrow 2ClF_3$. Thus, $\mathbf{Z} = ClF_3$.

Analysis of options:

(A) $Cl_2$ is well known for its disinfectant properties and is used for sterilizing drinking water. Correct.

(B) $NCl_3$ has $sp^3$ hybridization with one lone pair on nitrogen, resulting in a pyramidal structure, not planar. Incorrect.

(C) $ClF_3$ is used as a fluorinating agent to produce $UF_6$ from $U$ for the gaseous diffusion process of $^{235}U$ enrichment. Correct.

(D) In $NCl_3$, the electronegative chlorine atoms exert a strong inductive effect ($-I$), reducing the electron density on Nitrogen compared to $NH_3$, making it a much weaker Lewis base. Incorrect.