Solutions

Which of the following statements are not correct? Choose the correct answer from the options given below :

1. A and B only
2. A and D only
3. A, B and D only
4. A, C and D only

19.5 g of fluoro acetic acid (molar mass = 78 g mol-1) is dissolved in 500 g of water at 298 K. The depression in the freezing point of water was 1°C. What is Ka of fluoro acetic acid ? (For water, Kf = 1.86 K kg mol-1). Assume molarity and molality to have same values.

1. 10-6
2. 4 10-4
3. 3 10-5
4. 3 10-3

'W' g of a non-volatile electrolyte solid solute of molar mass 'M' g mol-1 when dissolved in 100 mL water, decreases vapour pressure of water from 640 mm Hg to 600 mm Hg. If aqueous solution of the electrolyte boils at 375 K and Kb for water is 0.52 K kg mol-1, then the mole fraction of the electrolyte solute (x2) in the solution can be expressed as (Given : density of water = 1 g/mL and boiling point of water = 373 K)

1. 162.6 WM
2. 1.38 MW
3. 2.616 MW
4. 1.38 WM

HA(aq) H+(aq) + A-(aq) The freezing point depression of a 0.1 m aqueous solution of a monobasic weak acid HA is 0.20 C. The dissociation constant for the acid is Given: Kf(H2O) = 1.8 K kg mol-1, molality ≡ molarity

1. 1.90 10-3
2. 1.38 10-3
3. 1.1 10-2
4. 1.89 10-1

1.24 g of AX2 (molar mass 124 g mol-1) is dissolved in 1 kg of water to form a solution with boiling point of 100.0156°C, while 25.4 g of AY2 (molar mass 250 g mol-1) in 2 kg of water constitutes a solution with a boiling point of 100.0260°C. Kb(H2O) = 0.52 kg mol-1 Which of the following is correct?

1. AX2 and AY2 (both) are completely unionised.
2. AX2 and AY2 (both) are fully ionised.
3. AX2 is completely unionised while AY2 is fully ionised.
4. AX2 is fully ionised while AY2 is completely unionised.

CrCl3 xNH3 can exist as a complex. 0.1 molal aqueous solution of this complex shows a depression in freezing point of 0.558 C. Assuming 100% ionisation of this complex and coordination number of Cr is 6, the complex will be (Given Kf = 1.86 K kg mol-1)

1. [Cr(NH3)5Cl]Cl2
2. [Cr(NH3)4Cl2]Cl
3. [Cr(NH3)6]Cl3
4. [Cr(NH3)3Cl3]

Arrange the following solutions in order of their increasing boiling points. (i) 10-4 M NaCl (ii) 10-4 M Urea (iii) 10-3 M NaCl (iv) 10-2 M NaCl

1. (i) < (ii) < (iii) < (iv)
2. (ii) < (i) < (iii) < (iv)
3. (iv) < (iii) < (i) < (ii)
4. (ii) < (i) (iii) < (iv)

We have three aqueous solutions of NaCl labelled as 'A', 'B' and 'C' with concentration 0.1 M, 0.01 M and 0.001 M, respectively. The value of van 't Hoff factor (i) for these solutions will be in the order :

1. iA < iC < iB
2. iA < iB < iC
3. iA > iB > iC
4. iA = iB = iC

The solution from the following with highest depression in freezing point/lowest freezing point is

1. 180 g of acetic acid dissolved in benzene
2. 180 g of acetic acid dissolved in water
3. 180 g of benzoic acid dissolved in benzene
4. 180 g of glucose dissolved in water