Which one of the following elements is unable to form $M{F}_6^{-3}$ ion?

• Ga

• Al

• In

• B

Which of the following statements is not true for halogens?

• All form monobasic oxyacids

• All are oxidizing agents

• Chlorine has the highest electron-gain enthalpy

• All but fluorine show positive oxidation states

In the structure of ClF₃, the number of lone pair of electrons on central atom ‘Cl’ is

• One

• Two

• Three

• Four

Which of the following oxide is most acidic?

• As₂O₃

• P₂O₅

• Sb₂O₃

• Bi₂O₃

when CO₂ is bubbled through a solution of barium peroxide in water then

• Carbonic acid is formed

• O₂ is released

• H₂O₂

• No reaction occurs

Among the following compounds, which will produce POCl₃ with PCl₅

• Only O₂

• O₂ and CO₂

• CO₂, O₂ and P₄O₁₀

• SO₂, H₂O, H₂SO₄ and P₄O₁₀

47.

In which of the following compounds, sulphur show maximum oxidation number?

• H₂SO₄

• SO₃

• H₂S₂O₇

• All have same oxidation number for sulphur

Consider the reaction, H₂ + X₂ $\to$ 2HX, where X is halogen. The reactivity of halogens decrease in the order of

• Cl₂ > F₂ > Br₂ > I₂

• I₂ > Br₂ > F₂ > Cl₂

• F₂ > Cl₂ > Br₂ > I₂

• I₂ > Br₂ > Cl₂ > F₂

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