1. | \(242.8 \mathrm{~g} \mathrm{~mol}^{-1}\) | 2. | \(238.2 \mathrm{~g} \mathrm{~mol}^{-1}\) |
3. | \(241.8 \mathrm{~g} \mathrm{~mol}^{-1}\) | 4. | \(240.0 \mathrm{~g} \mathrm{~mol}^{-1}\) |
The freezing point of depression constant (Kf ) of benzene is 5.12 K kg mol–1. The freezing point depression for the solution of molality 0.078 m containing a non-electrolyte solute in benzene is:
(rounded off up to two decimal places)
1. 0.80 K
2. 0.40 K
3. 0.60 K
4. 0.20 K
The freezing point depression constant for water is 1.86 oC m-1. If 5.00 g Na2SO4 is dissolved in 45.0 g H2O,
the freezing point is changed by -3.82 oC. The Van’t Hoff factor for Na2SO4 is:
1. | 2.63 | 2. | 3.11 |
3. | 0.381 | 4. | 2.05 |
A 0.1 molal aqueous solution of a weak acid (HA) is 30 % ionized. If Kf for water is 1.86 °C/m, the freezing point of the solution will be:
1. | –0.24 °C | 2. | –0.18 °C |
3. | –0.54 °C | 4. | –0.36 °C |
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 oC
2. –0.520 oC
3. +0.372 oC
4. –0.570 oC
A 0.0020 m aqueous solution of an ionic compound Co(NH3)5(NO2)Cl freezes at -0.0073 oC. The number of moles of ions that 1 mol of ionic compound produces on being dissolved in water will be:
(Kf = -1.86 oC/m)
1. | 2 | 2. | 3 |
3. | 4 | 4. | 1 |
0.5 molal aqueous solution of a weak acid (HX) is 20 % ionised. The lowering in the freezing point of the solution will be:
[Kf for water = 1.86 K kg mol-1]
1. -1.12 K
2. 0.56 K
3. 1.12 K
4. -0.56 K
A solution of urea (molar mass 56 g mol–1) boils at 100.18 ºC at atmospheric pressure. If Kf and Kb for water are 1.86 and 0.512 K kg mol–1 respectively, the above solution will freeze at:
1. –6.54 ºC
2. –0.654 ºC
3. 6.54 ºC
4. 0.654 ºC