Which of the following acids is used to manufactrure glass shell of television tubes?

Options

A. `HCl`
B. `HBr`
C. `HF`
D. `HI`

Answer

3

Explanation

Hydrofluorine acid attacks glass and hence is used for etching glass and manufacture of glass shell of television tubes.
It is also used for picking steel and making many fluorides:
`B_(2)O_(3)+6HF underset(H_(2)SO_(4))overset("conc.")rarr2BF_(3)+3H_(2)SO_(4).H_(2)O`
`Al_(2)O_(3)+6HF rarr 2AlF_(3)+3H_(2)O`
`NaCl+HF rarr NaF+HCl`
Anhydrogen `HF` is used as an alkyalation catalyst in the petrochemical industry.for making long chain alkyl- benzene compound s.These are then coverted into alkyl-benzene sulphoates and used as detergents. Smaller amounts of `HF` are used for uranium processing through intermediates `UF_(4)` and `UF_(6)`
it is used for making synthetic cryolite which is used in the electrolytic extraction of `Al`. It is also used for making chlorofluorocarbons (Freons).sometimes called `CFCs`.
`C Cl_(4)+2HF underset("conditions") overset("anhyhydrous")rarr underset("Freon -12")(C Cl_(2)F_(2))+2HCl`
They are used as refrigerating fluids and as the propellant is acrososls .However, the use of `CFCs` is being phase out because they demage the ozone layer in the uper atmosphere.