Question

Two metals $X$ and $Y$ form covalent halides. Both halides can act as Lewis acids and a catalyst in Friedel Crafts reaction. Halide of $X$ is polymer in the solid state and a dimer in the vapour state which decomposes to monomer at $1200K$. However, halide of $Y$ is a dimer in vapour state and becomes ionic in polar solvent. $X$ and $Y$ are respectively.

• A. Be, Al
• B. Al, Be
• C. Be, Ca
• D. Mg , Ca

Answer 1

Answer: (A)

Covalent halides are formed by $Be$ and $Al$ among the metals given. The halide of $Al,$ ie, $A{l}_{2}C{l}_6$ becomes ionic in polar solvent. Hence $Y$ is $Al.$ Halide of $Be$ is a polymer in solid state. Thus $X$ is $Be$.