21.

The made of nitrogen formed by thermal decomposition of NH₄NO₃ is

• NO

• N₂O

• N₂O₅

• NO₂

Which one of the following is most acidic?

• H₂O

• H₂S

• H₂Te

• H₂Se

Which one of the following is formed apart from sodium chloride when chlorine reacts with hot concentrated sodium hydroxide?

• NaOCl

• NaClO₃

• NaClO₂

• NaClO₄

Helium mixed with oxygen is used in the treatment of

• beri beri

• burning feet

• joints burning

• asthma

Which of the following is a correct statement?

• Aqueous solutions of Cu⁺ and Zn²⁺ are colourless

• Aqueous solutions of Cu²⁺ and Zn²⁺ are colourless

• Aqueous solution of Fe³⁺ is green in colour

• Aqueous solution of MnO^-₄ is colourless

The chemical reaction that involves roasting process is

• Fe₂O₃ + 3CO → 2Fe + 3CO₂

• 2Al + Fe₂O₃ → 2Fe + Al₂O₃

• 2ZnS + 3O₂ → 2ZnO + 3SO₂

• FeO + SiO₂ → FeSiO₃

The ratio of anion radius to cation radius of a crystal is 10 : 9.3. Then, the coordination number of the cation in the crystal is

• 2

• 6

• 4

• 8

If BaCl₂,ionizes to an extent of 80% in aqueous solution, the value of van't Hoff factor is

• 2.6

• 0.4

• 0.8

• 2.4

X is a non-volatile solute and Y is a volatile solvent. The following vapour pressures are observed by dissolving X in Y.

The correct order of vapour pressures is

• p₁ < p₂ <p₃

• p₃ < p₂ < p₁

• p₃ <p₁ < p₂

• p₂ <p₁ <p₃

At a certain temperature and at infinite dilution, the equivalent conductances of sodium benzoate, hydrochloric acid and sodium chlonde are 240, 349 and 229 ohm^-1 cm²equiv^-1 respectively. The equivalent conductance of benzoic acid in ohm^-1 cm²equiv^-1 at the same conditions is

• 80

• 328

• 360

• 408