21.

The carbonate that will not decompose on heating is

• Na₂CO₃

• CaCO₃

• BaCO₃

• SrCO₃

Which among the following statements are correct?

(i) Carbon monoxide is neutral whereas SO₃ is acidic.

(ii) Potassium oxide is basic whereas nitrous oxide is acidic.

(iii) Aluminium and zinc oxides are amphoteric.

(iv) Sulphur trioxide is acidic whereas phosphorus pentoxide is basic.

(v) Carbon dioxide is netural whereas sulphur dioxide is amphoteric.

• (ii) and (iii)

• (i) and (iv)

• (i) and (iii)

• (ii) and (iv)

When hydrogen peroxide is added to acidified potassium dichromate, a blue colour is produced due to formation of

• CrO₃

• Cr₂O₃

• CrO₅

• CrO${}_4^{2-}$

The pH of a neutral water is 6.5. Then the temperature of water

• is 25°C

• is more than 25°C

• is less than 25°C

• can be more or less than 25°C

If the elevation in boiling point of a solution of 10g of solute (mol. wt. = 100) in 100g of water is $∆$T_b, the ebullioscopic constant of water is 

• 10

• 100 T_b

• $∆$T_b

• 10 T_b

An alloy of Pb-Ag weighing 1.08 g was dissolved in dilute HNO₃ and the volume made to 100 mL. A silver electrode was dipped in the solution and the emf of the cell set up Pt(s), H₂ (g)| H⁺ (1M) || Ag⁺ (aq) | Ag(s) was 0.62V. If E^°_cell = 0. 80V. What is the percentage of Ag in the alloy? [At 25°C, RT / F = 0.06]

• 50

• 25

• 2.50

• 10

The standard oxidation potentials of Zn, Cu, Ag and Ni electrodes are +0.76, 0.34, -0.80 and +0.25 V respectively. Which of the following reaction will provide maximum voltage?

• Cu + 2Ag⁺(aq) → Cu²⁺(aq) + 2Ag

• Zn + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag

• H₂ + Ni²⁺(aq) → 2H⁺(aq) + Ni

• Zn + Cu²⁺(aq) → Zn²⁺(aq) + Cu

At 500 K, the half-life period of a gaseous reaction at an initial pressure of 80 kPa is 350 s. When the pressure is 40 kPa, the half-life period is 175 s. The order of the reaction is

• zero

• one

• two

• three

On adding 1 mL of solution of 10% NaCl to 10 mL of gold sol in the presence of 0.25 g of starch, the coagulation is just prevented. The gold number of starch is

• 250

• 25

• 2.5

• 0.25

Which of the following statements is not correct?

• The complexes [NiCl₄]^2- and [Ni(CN)₄]^2- differ in the state of hybridization of nickel

• The complexes [NiCl₄]^2- and [Ni(CN)₄]^2- differ in the magnetic properties

• The complexes [NiCl₄]^2- and [Ni(CN)₄]^2- differ in geometry

• The complexes [NiCl₄]^2- and [Ni(CN)₄]^2- differ in primary valencies of nickel