Why do we apply paint on iron articles?

What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer.

Write a balanced chemical equation with state symbols for the following reactions.
$(i)$ Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
$(ii)$ Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Why is respiration considered an exothermic reaction? Explain.

Write the balanced chemical equations for the following reactions.
$(a)$ Calcium hydroxide $+$ Carbon dioxide $\rightarrow$ Calcium carbonate $+$ Water
$(b)$ Zinc $+$ Silver nitrate $\rightarrow$ Zinc nitrate $+$ Silver
$(c)$ Aluminium $+$ Copper chloride $\rightarrow$ Aluminium chloride $+$ Copper
$(d)$ Barium chloride $+$ Potassium sulphate $\rightarrow$ Barium sulphate $+$ Potassium chloride