Which substance is formed when ammonia gas reacts with hydrogen chloride gas?

What type of reaction occurs when sulfur dioxide $(SO_2)$ reacts with an acidic solution of potassium dichromate $(K_2Cr_2O_7)$?

Which of the following methods is $NOT$ a method for the refining of metals?

In which of the following,is a displacement reaction possible?

Explain the following:
$(a)$ $NaCl$ is not a conductor of electricity in solid state,whereas it does conduct electricity in aqueous solution as well as in molten state.
$(b)$ Iron articles are galvanised.
$(c)$ Metals like $Na, K, Ca$ and $Mg$ are never found in their free state in nature.

During the electrolytic refining of zinc,it gets