Give a balanced equation for addition of iron to copper [II] sulphate solution. State the change in color seen.

In certain reactions a change of state is observed i.e. solid to liquid, liquid to gas etc. – State the change of state of the reactants – to give the respective products in each case.

(a) C + 2S ⟶ CS₂

(b) NH₃ + HCl ⇌ NH₄Cl

(c) 2H₂ + O₂ ⟶ 2H₂O

(d) $2\text{H}$2\text{O} \xrightarrow[\text{current}]{\text{electric}} 2\text{H}2 + \text{O}_2

In certain reactions an insoluble solid called precipitate is formed. State the colour and name of the precipitate formed in each of the following reactions involving addition of:

(a) Dilute hydrochloric acid to silver nitrate

(b) Iron [II] sulphate to sodium hydroxide

(c) Iron [III] chloride to ammonium hydroxide

(d) Copper [II] sulphate to sodium hydroxide

(e) Lead nitrate to ammonium hydroxide

Give examples of exothermic reactions i.e. heat evolved in each of the following:

(a) reaction between a solid and a liquid

(b) reaction between two gases

Give two examples of exothermic reactions seen in everyday life.