Question

A compound $MC{l}_3$, where $M$ is an unknown element, has a melting point of $-{92}^{\circ }C$.
The compound can be identified as which of the following?

• A. Aluminum chloride
• B. Phosphorus trichloride
• C. Gold chloride
• D. Iron (III) chloride

Answer 1

The correct option is B Phosphorus trichloride

Melting point of covalent compounds is quite low due weak intermolecular forces between them compared to ionic bond.

Here $MC{l}_3$has melting point of $-{92}^{o}c$ which is quite low,So,$M$ must be a nonmetal with oxidation state$+3$.

$M$will be phosphorous and $MC{l}_3$ is $PC{l}_3$