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:

A 0.1 molal aqueous solution of a weak acid (HA) is 30 % ionized. If K_f for water is 1.86 °C/m, the freezing point of the solution will be:

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: 
(k_f 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:
(K_f = -1.86 ^oC/m)

0.5 molal aqueous solution of a weak acid (HX) is 20 % ionised. The lowering in the freezing point of the solution will be:
[K_f for water = 1.86 K kg mol^-1]

1. -1.12 K

2. 0.56 K

3. 1.12 K

4. -0.56 K