What is the molecular formula of cryolite?

What is ammonium hydroxide $(NH_4OH)$?

Who discovered hydrogen gas?

$(a)$ List two differences between calcination and roasting in tabular form.
$(b)$ Which method will you use to reduce the following? Explain by giving a suitable example.
$(i)$ Oxides of less reactive metals.
$(ii)$ Oxides of moderately reactive metals.
$(iii)$ Oxides of highly reactive metals.

Which alloy is used to solder electric wires?

Name the metal which:
$(a)$ becomes blackish after a certain time.
$(b)$ develops a green coating on exposure to air.
$(c)$ does not corrode at all.
$(d)$ is used in making steel.
$(e)$ is non-lustrous.