In the context of the lanthanoids, which of the following statement is not correct?

• There is a gradual decrease in the radii of the members with increasing atomic number in the series. 

• All the member exhibit +3 oxidation state.

• Because of similar properties, the separation of lanthanoids is not easy.

• Because of similar properties, the separation of lanthanoids is not easy.

The freezing point of benzene decreases by 0.45°C when 0.2 g of acetic acid is added to 20 g of benzene. If acetic acid associates to form a dimer in benzene, percentage association of acetic acid in benzene will be
(K_f for benzene = 5.12 K kg mol^–1)

• 64.6% 

• 80.4%

• 74.6%

• 74.6%

A vessel at 1000 K contains CO₂ with a pressure of 0.5 atm. Some of the CO₂ is converted into CO on the addition of graphite. If the total pressure at equilibrium is 0.8 atm, the value of K is

• 1.8 atm

• 3 atm

• 0.3 atm

• 0.3 atm

If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution, the change in freezing point of water (ΔT_f), when 0.01 mol of sodium sulphate is dissolved in 1 kg of water, is (K_f = 1.86 K kg mol^–1).

• 0.0372 K

• 0.0558 K

• 0.0744 K

• 0.0744 K

On mixing, heptane and octane form an ideal solution. At 373 K, the vapour pressures of the two liquid components (heptane and octane) are 105 kPa and 45 k_Pa respectively.Vapour pressure of the solution obtained by mixing 25.0 g of heptane and 35 g of octane will be (molar mass of heptane = 100 g mol^–1 and of octane =114 g mol^–1)

• 144.5 kPa

• 72.0 kPa

• 36.1 kPa

• 36.1 kPa