Solutions

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

During osmosis, flow of water through a semipermeable membrane is

1. from solution having lower concentration only
2. from solution having higher concentration only
3. from both sides of semipermeable membrane with equal flow rates
4. from both sides of semipermeable membrane with unequal flow rates.

A solution of acetone in ethanol

1. obeys Raoult's law
2. shows a negative deviation from Raoult's law
3. shows a positive deviation from Raoult's law
4. behaves like a near ideal solution.

1.00 g of a non-electrolyte solute (molar mass 250 g mol-1) was dissolved in 51.2 g of benzene. If the freezing point depression constant, Kf of benzene is 5.12 K kg mol-1, the freezing point of benzene will be lowered by

1. 0.2 K
2. 0.4 K
3. 0.3 K
4. 0.5 K

A solution containing 10 g per dm3 of urea (molecular mass = 60 g mol-1) is isotonic with a 5% solution of a nonvolatile solute. The molecular mass of this nonvolatile solute is

1. 200 g mol-1
2. 250 g mol-1
3. 300 g mol-1
4. 350 g mol-1