21.

The product obtained as a result of a reaction of nitrogen with CaC₂ is 

• CaCN

• CaCN₃

• Ca₂CN

• Ca₂CN

Fog is a colloidal solution of 

• Gas in liquid

• Solid in gas

• Gas in gas

• Gas in gas

Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules?

• Cl₂>Br₂>F₂>I₂

• Br₂>I₂>F₂>Cl₂

• F₂>Cl₂>Br₂>I₂

• F₂>Cl₂>Br₂>I₂

Lithium has a bcc structure. Its density is 530 kg m^-3 and its atomic mass is 6.94 g mol^-1. Calculate the edge length of a unit cell of lithium metal. (N_A = 6.02 x 10²³ mol^-1).

• 352pm

• 527pm

• 264pm

• 264pm

Which of the following statements about the composition of the vapour over an ideal 1:1 molar mixture of benzene and toluene is correct? Assume that the temperature is constant at 25⁰C.
(Given, vapour pressure data at 25⁰C benzene = 12.8 kPa, toluene = 3.85 kPa)

• The vapour will contain a higher percentage of toluene

• The vapour will contain equal amounts of benzene and toluene

• Not enough information is given to make a prediction

• Not enough information is given to make a prediction

The rate of a first-order reaction is 0.04 mol L^-1s^-1 at 10 sec and 0.03 mol^-1L^-1 s^-1 at 20 sec after initiation of the reaction. the half-life period of the reaction is 

• 34.1 s

• 44.1 s

• 54.1 s

• 54.1 s

The ionic radii of A⁺ and B^- ions are 0.98 x 10^-10 m and 1.81 x10^-10 m. The coordination number of each ions in AB is 

• 4

• 8

• 2

• 2

Which of the following has longest C-O bond length? (free C-O bond length in CO is 1.128 A⁰)

• [Co(CO)₄]^-

• [Fe(CO)₄]^-2

• [Mn(CO)₆]⁺

• [Mn(CO)₆]⁺

Among the following, the correct order of acidity is

• HClO<HClO₂<HClO₃<HClO₄

• HClO₂<HClO<HClO₃<HClO₄

• HClO₄<HClO<HClO <HClO₃

• HClO₄<HClO<HClO <HClO₃

The pressure of H₂ required to make the potential of H₂-electrode zero in pure water at 298 K is

• 10^-12 atm

• 10^-10 atm

• 10^-4 atm

• 10^-4 atm