Question 13.24:-

Suggest the name of a Lewis acid other than anhydrous aluminum chloride which can be used during ethylation of benzene.

The methylation reaction of benzene involves the addition of an ethyl group on the benzene ring. Such a reaction is called a Friedel-Craft alkylation reaction. This reaction takes place in the presence of a Lewis acid.
Any Lewis acid like anhydrous FeCl3, SnCl4, BF3, etc. can be used during the ethylation of benzene