What happens when a piece of $Zn$ metal is added to $CuSO_4$ solution?

Translate the following statements into chemical equations and then balance them.
$(a)$ Hydrogen gas combines with nitrogen to form ammonia.
$(b)$ Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

"$A$ solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed".
$(i)$ Translate the above statement into a chemical equation.

Which among the following statement$(s)$ is(are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to:
$(i)$ The formation of silver by decomposition of silver chloride
$(ii)$ Sublimation of silver chloride
$(iii)$ Decomposition of chlorine gas from silver chloride
$(iv)$ Oxidation of silver chloride

State the reason for the following:
$(a)$ Potato chips manufacturers usually flush bags of chips with nitrogen gas.
$(b)$ Iron articles lose their shine gradually.
$(c)$ Foods should be kept in airtight containers.

Which among the following changes are exothermic or endothermic in nature?
$(a)$ Decomposition of ferrous sulphate
$(b)$ Dilution of sulphuric acid
$(c)$ Dissolution of sodium hydroxide in water
$(d)$ Dissolution of ammonium chloride in water