Question

Which of the following statement(s) regarding $PC{l}_3$ is/are true?

• A. $PC{l}_3$ acts as a reducing agent when treated with $S{O}_3$ and conc. $H_{2}S{O}_4$​
• B. $PC{l}_3$ does not react with organic compounds
• C. $PC{l}_3$ is a colourless oily liquid
• D. $PC{l}_5$ decompose at ${250}^{o}C$ to $PC{l}_3$

Answer 1

Answer: (A), (C), (D)

$PC{l}_5$ decompose at ${250}^{o}C$ to $PC{l}_3$

$PC{l}_3$ is a colourless oily liquid.

It act as a reducing agent when treated with $S{O}_3$ and $conc.H_{2}S{O}_4$.

$PC{l}_3+S{O}_3\to POC{l}_3+S{O}_2$
$PC{l}_3+2H_{2}S{O}_4\to S{O}_{3}HCl+S{O}_2+2HCl+HP{O}_3$

$S{O}_{3}HCl$ is chlorosulphonic acid

Phosphorus trichloride is widely used as an important reagent in organic chemistry for replacing hydroxyl groups by chlorine atoms in organic reactions. For example, ethanol reacts with phosphorus trichloride to form chloroethane and phosphorous acid.
$3C{H}_{3}C{H}_{2}OH+PC{l}_3\to 3C{H}_{3}C{H}_{2}Cl+H_{3}P{O}_3$

$PC{l}_5$ sublimes when it is heating but it start to decompose on stronger heating.
$PC{l}_5\stackrel{{250}^{o}C}{\to }PC{l}_3+C{l}_2$
Hence, statements (a), (c) and (d) are correct.