A reaction of a type: AB + CD ⟶ AD + CB, involves

(i) no chemical change

(ii) decomposition of AB and CD

(iii) exchange of ions of AB and CD

(iv) combination of AB and CD

The reaction:

BaCl₂ (aq) + H₂SO₄ (aq) ⟶ BaSO₄ (s) + 2HCl (aq) is

(i) displacement reaction

(ii) neutralisation reaction

(iii) decomposition reaction

(iv) double displacement reaction

Match the following :

Complete the following statements.

(a) The chemical change involving iron and hydrochloric acid illustrates a …………… reaction.

(b) In the type of reaction called …………… two compounds exchange their positive and negative radicals.

(c) A catalyst either …………… or …………… the rate of a chemical change but itself remains …………… at the end of the reaction.

(d) On heating, hydrated copper sulphate changes its colour from …………… to ……………