The mass of a non-volatile solute (molar mass 40 g mol^–1) that should be dissolved in 114 g octane to reduce its vapour pressure to 80 % would be:

1. 6 g

2. 7 g

3. 8 g

4. 10 g

Benzene and toluene form an ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively.

The mole fraction of benzene in vapour phase, if 80 g of benzene is mixed with 100 g of toluene, would be:

1. 0.41

2. 0.68

3. 0.72

4. 0.59

The vapour pressure of 1 molal solution of a non-volatile solute in water at 300 K would be:

(The vapour pressure of water at 300 K = 12.3 kPa)