Question

A translucent white waxy solid (A) reacts with excess of chlorine to give a yellowish white powder (B). (B) reacts with organic compounds containing -OH group converting them into chloro derivatives. (B) on hydrolysis gives (C) and is finally converted to phosphoric acid. (A), (B) and (C) are?
(a)- ${{P}_{4}}$, $PC{{l}_{3}}$, ${{H}_{3}}P{{O}_{4}}$
(b)- ${{P}_{4}}$, $PC{{l}_{5}}$, ${{H}_{3}}P{{O}_{3}}$
(c)- ${{P}_{4}}$, $PC{{l}_{5}}$, $POC{{l}_{3}}$
(d)- ${{P}_{4}}$, $PC{{l}_{3}}$, $POC{{l}_{3}}$

Answer 1

Phosphorus is a reactive nonmetal with atomic number 15. It also shows the property of allotropy or allotropism. Most common allotropes of phosphorus are:
- White Phosphorus
- Red Phosphorus
- Black Phosphorus

Complete step by step answer:
White Phosphorus is ${{P}_{4}}$ molecules packed into a crystal at a bond angle of 60 degree. They have a white waxy solid like appearance at room temperature.
${{P}_{4}}$ reacts with excess of chlorine to give a yellowish or off-white powder of phosphorus pentachloride.
$\underset{\mathbf{A}}{\mathop{{{P}_{4}}\,}}\,+10C{{l}_{2}}\to 4\underset{\mathbf{B}}{\mathop{PC{{l}_{5}}}}\,$
Solid phosphorus pentachloride reacts violently with organic compounds containing -OH group (alcohols) at room temperature, producing clouds of hydrogen chloride gas. It is used as a test for -OH groups in organic chemistry.
$\underset{\mathbf{B}}{\mathop{PC{{l}_{5}}}}\,+ROH\to RCl+POC{{l}_{3}}$
For example:
$C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}OH+PC{{l}_{5}}\to C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}Cl+POC{{l}_{3}}+HCl$
Phosphorus pentachloride is hydrolyzed to form $POC{{l}_{3}}$ which on further hydrolysis gives phosphoric acid ${{H}_{3}}P{{O}_{4}}$.

& \underset{\mathbf{B}}{\mathop{PC{{l}_{5}}}}\,+{{H}_{2}}O\to \underset{\mathbf{C}}{\mathop{POC{{l}_{3}}}}\,+2HCl \\\ & POC{{l}_{3}}+{{H}_{2}}O\to {{H}_{3}}P{{O}_{4}}+3HCl \\\ \end{aligned}$$ So, the correct option is (c). **Note:** White Phosphorus $${{P}_{4}}$$ burns spontaneously in chlorine to produce a mixture of two chlorides depending on the amount of Chlorine. In a limited amount of Chlorine, it forms phosphorus trichloride. Phosphorus trichloride is a colorless fuming liquid. $${{P}_{4}}\,+6C{{l}_{2}}\to 4PC{{l}_{3}}$$