Sodium sulphite is used in preserving squashes and other mildly acidic foods due to

• potassium salt has preservative action

• potassium metabisulphite prevents oxidation

• potassium metabisulphite is not influcenced by acid

• sulphur dioxide and sulphurous acid formed, kill bacteria and germs

The major role of fluorspar (CaF₂) which is added in small quantity in the electrolytic reduction of alumina dissolved in fused cryolite (Na₃AlF₆) is

I. as a catalyst.

II. to make the fused mixture very conducting.

III. to lower the temperature of melting.

IV. to decrease the rate of oxidation of carbon at the anode.

• I, II

• II, III

• I, II, III

• III, IV

593.

Noble gases are used in discharge tubes to give different colours. Reddish-orange glow is due to

• Ar

• Ne

• Xe

• Kr

T-shaped inter halogen compound is:

• ClF₃

• ICl

• ClF₅

• IF₅

The correct order of acid strength is

• HClO < HClO₂ < HClO₃ < HClO₄

• HClO₄ < HClO < HClO₂ < HClO₃

• HClO₂ < HClO₃ < HClO₄ < HClO

• HClO₄ < HClO₃ < HClO₂ < HClO

Which of the following molecules forms no inter molecular hydrogen bonds?

• ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}$

• HF

• ${\mathrm{CH}}_3{\mathrm{COCH}}_3$

• ${\mathrm{CH}}_3\mathrm{COOH}$

Which of the following metals, Fe, Zn, Pb, Ag and Pt do not give a metal nitrate on treatment with concentrated HNO?

• Fe and Zn.

• Fe and Pt.

• Pb, Ag and pt.

• Fe, Ag and Zn.

The oxidation number of sulphur atoms in peroxomonosulphuric acid H₂SO₅ and peroxodisulphuric acid H₂S₂O₈, respectively are:

• +8 and +7

• +6 and +6

• +4 and +6

• +3 and +3

When aqueous ammonia is added to green solution of nickel chloride, the colour changes to:

• yellow

• purple

• violet

• violet

Organophosphorus compounds are the most toxic insecticides. The common organophosphorus insecticides is:

• Methoxy chlor

• Dieldrin

• Parathion

• Malathion