Oil and fat containing food items are flushed with nitrogen. Why?

Balance the following chemical equations:
$(a)$ $HNO_{3} + Ca(OH)_{2} \longrightarrow Ca(NO_{3})_{2} + H_{2}O$
$(b)$ $NaOH + H_{2}SO_{4} \longrightarrow Na_{2}SO_{4} + H_{2}O$
$(c)$ $NaCl + AgNO_{3} \longrightarrow AgCl + NaNO_{3}$
$(d)$ $BaCl_{2} + H_{2}SO_{4} \longrightarrow BaSO_{4} + HCl$

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.

Write the balanced chemical equations for the following reactions:
$(i)$ Hydrogen $+$ Chlorine $\to$ Hydrogen chloride
$(ii)$ Barium chloride $+$ Aluminium sulphate $\to$ Barium sulphate $+$ Aluminium chloride
$(iii)$ Sodium $+$ Water $\to$ Sodium hydroxide $+$ Hydrogen

What does one mean by exothermic and endothermic reactions? Give examples.

Why should a magnesium ribbon be cleaned before burning in air?