Which metal can be beaten into very thin foils?

What is the color of a potassium dichromate solution?

Which gas is used in the process of converting vegetable oils into vegetable ghee?

Who discovered hydrogen gas?

$(a)$ When calcium metal is added to water,the gas evolved does not catch fire,but the same gas evolved on adding potassium metal to water catches fire. Explain why?
$(b)$ Name a metal for each case:
$(i)$ It displaces hydrogen gas from nitric acid.
$(ii)$ It does not react with any physical state of water.
$(iii)$ It does not react with cold as well as hot water but reacts with steam.

By which method/process is ammonia gas manufactured?