Question

Choose the correct statements from the following.

(i) Beryllium is not readily attacked by acids because of the presence of an oxide film on the surface of the metal.

(ii) Beryllium sulphate is readily soluble in water as the greater hydration enthalpy of Be²⁺ overcomes the lattice enthalpy factor.

(iii) Beryllium exhibits coordination number more than four.

(iv) Beryllium oxide is purely acidic in nature.

Answer 1

(i) Beryllium is not readily attacked by acids because of the presence of an oxide film on the surface of the metal.

(ii) Beryllium sulphate is readily soluble in water as the greater hydration enthalpy of Be²⁺ overcomes the lattice enthalpy factor.

Explanation:

(i) Beryllium resembles aluminium through the diagonal relation. Beryllium forms a protective film of oxide on the surface, and thus, is prevented by the attack of acids. Thus, statement is correct.

(ii) On moving down the group, as the size increases the hydration enthalpy decreases. The hydration enthalpy of beryllium ions are high due to the small size. Thus, sulfates are readily soluble in water. Thus, statement is correct.

(iii) Beryllium does not exhibit coordination numbers more than four. As it has no dd orbitals. Thus, statement is not correct.

(iv) Beryllium oxide is amphoteric in nature. It reacts with both acids and bases. It reacts with acid to form beryllium chloride and it reacts with base to form becyllate ion which is soluble in sodium hydroxide. The reaction is shown below.

$$\mathrm{Be}(\mathrm{OH}){\phantom{A}}_2+2\mathrm{OH}{\phantom{A}}^{-}⟶[\mathrm{Be}(\mathrm{OH}){\phantom{A}}_4]{\phantom{A}}^{2-}$$

$$\mathrm{Be}(\mathrm{OH}){\phantom{A}}_2+2\mathrm{HCl}⟶\mathrm{BeCl}{\phantom{A}}_2+2\mathrm{H}{\phantom{A}}_2\mathrm{O}$$

Thus, statement is not correct.