Which of the statements about the reaction below are incorrect ?

$2 PbO _{( s )}+ C _{( s )} \longrightarrow 2 Pb _{( s )}+ CO _{2( g )}$

$(a)$ Lead is getting reduced.

$(b)$ Carbon dioxide is getting oxidised.

$(c)$ Carbon is getting oxidised.

$(d)$ Lead oxide is getting reduced.

$Fe _{2} O _{3}+2 Al \rightarrow Al _{2} O _{3}+2 Fe$

The above reaction is an example of a 

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 sulpur dioxide.

$(c)$ Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

$(d)$ Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Why is the amount of gas collected in one of the test tubes in image double of the amount collected in the other ? Name this gas.

A shiny brown coloured element $‘X’$ on heating in air becomes black in colour. Name the element $‘X’$ and the black coloured compound formed.

Explain the "Reduction'' in terms of gain or loss of oxygen with two examples.