Hydrofluoric acid is not kept in a glass bottle because it reacts with

Correct answer: (d) Silicon dioxide of glass

Explanation

Hydrofluoric acid (HF) attacks the silicon dioxide (silica) in glass:

SiO₂ + 4HF → SiF₄ + 2H₂O

This etches and dissolves the glass, so HF is stored in plastic (polythene) or wax-lined bottles. The same reaction is used to etch designs on glass.