Solutions — Chemistry STD 12 Science — Question

Read the passage given below and answer the following questions: Boiling point or freezing point of liquid solution would be affected by the dissolved solids in the liquid phase. A soluble solid in solution has the effect of raising its boiling point and depressing its freezing point. The addition of non-volatile substances to a solvent decreases the vapor pressure and the added solute particles affect the formation of pure solvent crystals. According to many researches the decrease in freezing point directly correlated to the concentration of solutes dissolved in the solvent. This phenomenon is expressed as freezing point depression and it is useful for several applications such as freeze concentration of liquid food and to find the molar mass of an unknown solute in the solution. Freeze concentration is a high quality liquid food concentration method where water is removed by forming ice crystals. This is done by cooling the liquid food below the freezing point of the solution. The freezing point depression is referred as a colligative property and it is proportional to the molar concentration of the solution (m), along with vapor pressure lowering, boiling point elevation, and osmotic pressure. These are physical characteristics of solutions that depend only on the identity of the solvent and the concentration of the solute. The characters are not depending on the solute’s identity.

1. When a non volatile solid is added to pure water it will:

1. boil above 100°C and freeze above 0°C
2. boil below 100°C and freeze above 0°C
3. boil above 100°C and freeze below 0°C
4. boil below 100°C and freeze below 0°C

2. Colligative properties are:

1. dependent only on the concentration of the solute and independent of the solvent’s and solute’s identity.
2. dependent only on the identity of the solute and the concentration of the solute and independent of the solvent's identity.
3. dependent on the identity of the solvent and solute and thus on the concentration of the solute.
4. dependent only on the identity of the solvent and the concentration of the solute and independent of the solute’s identity.

3. Assume three samples of juices A, B and C have glucose as the only sugar present in them. The concentration of sample A, B and C are 0.1M, 5M and 0.2 M respectively. Freezing point will be highest for the fruit juice:

1. A
2. B
3. C
4. All have same freezing point

4. Identify which of the following is a colligative property:

1. freezing point
2. boiling point
3. osmotic pressure
4. all of the above