Solutions · Question 30

Vapour pressure of chloroform (CHCl3) and dichloromethane (CH2Cl2) at 25 are 200 mm Hg and 41.5 mm Hg respectively. Vapour pressure of the solution obtained by mixing 25.5 g of CHCl3 and 40 g of CH2Cl2 at the same temperature will be (Molecular mass of CHCl3 = 119.5 u and molecular mass of CH2Cl2 = 85 u)

1. 173.9 mm Hg
2. 615.0 mm Hg
3. 90.6 mm Hg
4. 285.5 mm Hg

pA and pB are the vapour pressures of pure liquid components, A and B, respectively of an ideal binary solution. If xA represents the mole fraction of component A, the total pressure of the solution will be

1. pA + xA (pB - pA )
2. pA + xA (pA - pB )
3. pB + xA (pB - pA )
4. pB + xA (pA - pB )

A 0.1 molal aqueous solution of a weak acid is 30% ionized. If Kf for water is 1.86 C/m, the freezing point of the solution will be

1. -0.18 C
2. -0.54 C
3. -0.36 C
4. -0.24 C

200 mL of an aqueous solution of a protein contains its 1.26 g. The osmotic pressure of this solution at 300 K is found to be 2.57 10-3 bar. The molar mass of protein will be (R = 0.083 L bar mol-1 K-1)

1. 51022 g mol-1
2. 122044 g mol-1
3. 31011 g mol-1
4. 61038 g mol-1

The freezing point depression constant for water is 1.86 C m-1. If 5.00 g Na2SO4 is dissolved in 45.0 g H2O, the freezing point is changed by -3.82 C. Calculate the van't Hoff factor for Na2SO4.

1. 2.05
2. 2.63
3. 3.11
4. 0.381

The van't Hoff factor i for a compound which undergoes dissociation in one solvent and association in other solvent is respectively

1. less than one and greater than one
2. less than one and less than one
3. greater than one and less than one
4. greater than one and greater than one

An aqueous solution is 1.00 molal in KI. Which change will cause the vapour pressure of the solution to increase?

1. Addition of NaCl
2. Addition of Na2SO4
3. Addition of 1.00 molal KI
4. Addition of water

A solution of sucrose (molar mass = 342 g mol-1) has been prepared by dissolving 68.5 g of sucrose in 1000 g of water. The freezing point of the solution obtained will be (Kf for water = 1.86 K kg mol-1)

1. -0.372 C
2. -0.520 C
3. +0.372 C
4. -0.570 C

A 0.0020 m aqueous solution of an ionic compound [Co(NH3)5(NO2)]Cl freezes at -0.00732 C. Number of moles of ions which 1 mol of ionic compound produces on being dissolved in water will be (Kf = 1.86 C/m)

1. 3
2. 4
3. 1
4. 2

0.5 molal aqueous solution of a weak acid (HX) is 20% ionised. If Kf for water is 1.86 K kg mol-1, the lowering in freezing point of the solution is

1. 0.56 K
2. 1.12 K
3. -0.56 K
4. -1.12 K