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

Hint: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 \[{{H}_{3}}P{{O}_{4}}\].
\[\begin{align}
  & \underset{\mathbf{B}}{\mathop{PC{{l}_{5}}}}\,+{{H}_{2}}O\to \underset{\mathbf{C}}{\mathop{POC{{l}_{3}}}}\,+2HCl \\
 & POC{{l}_{3}}+{{H}_{2}}O\to {{H}_{3}}P{{O}_{4}}+3HCl \\
\end{align}\]

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.
\[{{P}_{4}}\,+6C{{l}_{2}}\to 4PC{{l}_{3}}\]