Solutions Test - 6

Depression in freezing point is a colligative property but freezing point is not a colligative property.

The correct answer is Option B.
 
Molal elevation constant is a characteristic constant for a given solvent. It is the elevation of boiling point produced when one mole of solute is dissolved in 1 kg of solvent. The proportionality constant, Kb, is called the molal boiling point elevation constant. It is a constant that is equal to the change in the boiling point for a 1-molal solution of a nonvolatile molecular solute.

The correct answer is option A
The colligative properties of a solution are
Proportional to the number of solute particles present.
In chemistry, colligative properties are those properties of solutions that depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the nature of the chemical species present.

Elevation of boiling point and depression in freezing point are directly related to molality of solution.

Colligative properties- The properties that depend upon the ratio of the number of solute molecules and total molecules not upon the nature of solute molecules named as colligative properties.

Example- Osmotic pressure, elevation of boiling point, depression in freezing point and relative lowering of vapour pressure.

The correct answer is Option B.
A Beckmann 's thermometer is a device used to measure elevation in boiling point or depression in freezing point.

The correct answer is Option B.
 
∆T_b =(K_b ×1000 ×W₂ ) / M₂ ×W₁
⇒M₂ = (K_b ×1000 ×W₂ ) / ∆T_b ×W₁
= (1.71 ×1000 ×2) / 1 ×100
= 34.2g

The correct answer is option A
Due to solute presence in the solution, the solution 's boiling point is greater than the pure solvent 's boiling point. This is called as elevation in boiling point and it can be represented as:
ΔT_b ​=K_b ​×molality

The correct answer is option C  
ΔT_f = K_f  x m Since ΔT_f for 5m NaCl will be higher than for 2m, 5m NaCl solution freezes at a lower temperature.

The correct answer is option C
Relative lowering of vapour pressure:
= lowering of vapour pressure of solution/ vapour pressure of pure solvent
=0.0175/17.5=0.001

Molality (amount of moles per 1 kg of the solvent, mol/kg) and mole fraction (mol/mol) will remain constant since they are independent of volume of the solution which changes with temperature. Molarity i.e. amount of moles of a substance in 1 liter of a solution will change with volume of the solution so it will change with temperature.

Relative lowering of vapour pressure is directly proportional to mole fraction of solute. Hence it is a colligative property.
 

The correct answer is Option B.

When a non-volatile solute is dissolved in a pure solvent, its vapour pressure is decreased. The difference in the boiling points of the solution and pure solvent is called elevation in boiling point.
 
The elevation in the boiling point of a solution of nonelectrolyte is proportional to its molality and the equimolal solution of all the substances in the same solvent will show an equal elevation in boiling points. These are known as Raoult 's laws of elevation of the boiling point.
 
So, the addition of salt will increase the boiling point of the solution.
 

The correct answer is “molal depression constant is high ”.

Camphor is used for the determination of molecular masses of solute by Rast method because its molal depression constant is very high 40Kmolality^-1 .