Question

(a) Complete the following reaction equations:

(i) P₄ + NaOH + H₂O→

(ii) Cu + HNO₃ (dilute)→

(b) Explain why
(i) H₂O is a liquid while, inspite of a higher molecular mass, H₂S is a gas.
(ii) iron dissolves in HCl to form FeCl₂ and not FeCl₃.
(iii) helium is used in diving equipment

Answer 1

(b) (i) Because of small size and high electro negativity of oxygen, molecules of water are highly associated through H-bonding resulting in its liquid state.

(ii) Its reaction with iron produces H₂

Fe + 2HCl → FeCl₂ + H₂

Liberation of hydrogen prevents the formation of ferric chloride.
(iii) Because of its very low solubility in blood it prevents ‘bends