31.

If the elevation in boiling point of a solution of non-volatile, non-electrolytic and non-associating solute in a solvent (K_b = x K kg mol^-1) is y K, then the depression in freezing point of solution of same concentration would be (K_f of the solvent = z K kg mol^-1)

• $\frac{2xz}{y}$

• $\frac{yz}{x}$

• $\frac{xz}{y}$

• $\frac{yz}{2x}$

The vapour pressure of pure benzene and toluene at a particular temperature are 100 mm and 50 mm respectively. Then the mole fraction of benzene in vapour phase in contact with equimolar solution of benzene and toluene is 

• 0.67

• 0.75

• 0.33

• 0.50

When the total cell emf of a volatic cell is greater than zero, which of the following is true about the reaction quotient Q and free energy change $∆$G for the cell reaction?

• Q is less than one and $∆$G is greater than zero

• Q is greater than one and $∆$G is greater than zero

• Q is greater than one and $∆$G is less than zero

• Q is zero and $∆$G is greater than zero

The reaction, A + B → products is first order with respect to A and second order with respect to B. When 1.0 mole each of A and B were taken in one litre flask, the initial rate of the reaction is 1.0 × 10^-2 mol L^-1 s^-1. The rate of the reaction when 50% of the reactants have been converted into products is

• 1.00 × 10^-3 mol L^-1 s^-1

• 0.05 × 10^-2 mol L^-1 s^-1

• 1.25 × 10^-3 mol L^-1 s^-1

• 4.00 × 10^-2 mol L^-1 s^-1

For the following reaction,

NO₂(g) + CO(g) → NO(g) + CO₂(g)

the rate law is Rate = k [NO₂]². If 0.1 mole of gaseous carbon monoxide is added at constant temperature to the reaction mixture which of the following statement is true?

• Both k and the reaction rate remain the same

• Both k and the reaction rate increase

• Both k and the reaction rate decrease

• Only k increases, the reation rate remain the same

Which one of the following is an example for multimolecular colloid?

• Sulphur sol in water

• Aqueous starch sol

• Aqueous enzyme sol

• Alcoholic polystyrene sol

Which one of the following halogen compounds is difficult to be hydrolysed by S_N1 mechanism?

• Tertiary butyl chloride

• lsopropyl chloride

• Benzyl chloride

• Chlorobenzene

Compound 'A' of molecular formula C₄H₁₀O on treatment with Lucas reagent at room temperature gives compound 'B'. When compound 'B' is heated with alcoholic KOH, it gives isobutene. Compound 'A' and 'B' are respectively 

• 2-methyl-2-propanol and 2-methyl-2-chloropropane

• 2-methyl-1-propanol and 1-chloro-2-methylpropane

• 2-methyl- 1-propanol and 2-methyl-2-chloropropane

• butan-2-ol and 2-chlorobutane

Salicylaldehyde can be prepared from phenol by

• Scholten-Baumann reaction

• Kolbe's reaction

• Reimer-Tiemann reaction

• Perkin reaction

Which one of the following is not an allylic halide?

• 4-bromopent-2-ene

• 3-bromo-2-methylbut-1-ene

• 1-bromobut-2-ene

• 4-bromobyt-1-ene