" Halogen acid used for etching of glass is "

The acid used for etching of glass is

The acid used for etching the glass is

The acid used for etching the glass is

The acid used for etching the glass is :

What is etching of glass ?

Hydrolysis of compound A , two acids P and Q forms, P is used in etching of glass, Q on strongly heating gives a oxide R. R is used in estimation of carbon monoxide . Calculate total number of lone pairs on compound A .

Halogen acid used in the preparation of aqua regia is ………….