© examsnet.com
Question : 28
Total: 30
(a) Define the following terms:
(i) Molarity
(ii) Molal elevation constant( k b )
(b) A solution containing15 g = 60 g mol − 1 = 190 g mol − 1
OR
(a) What type of deviation is shown by a mixture of ethanol and acetone? Give reason.
(b) A solution of glucose (molar mass= 180 g mol − 1 10 % = 1.2 g mL − 1
(i) Molarity
(ii) Molal elevation constant
(b) A solution containing
OR
(a) What type of deviation is shown by a mixture of ethanol and acetone? Give reason.
(b) A solution of glucose (molar mass
Solution:
(a) (i) Molarity of a solution is defined as the number of moles of solute present in one litre of the solution.
(ii) Molal elevation constant( K b )
(b) Given; Mass of urea,W B = 15 g
Molar mass of urea,M urea = 60 g
The solution of urea in water is isotonic to that of glucose solution.
π urea = π glucose
C urea RT = C glucose RT
=
RT
=
W glucose =
W glucose = 45 g
OR
(a) According to Raoult's law, the partial pressure of a component is the product of vapour pressure of pure solvent and mole fraction of that component. When a solution shows deviation from Raoult's law over the complete range of concentration, the solution is known as a non-ideal solution.
The vapour pressure of the non-ideal solution can be higher or lower than the vapour pressure predicted by Raoult's law.
If the vapour pressure of the non-ideal solution is higher than the vapour pressure predicted by Raoult's law, the deviation is known as positive deviation.
If the vapour pressure of the non-ideal solution is lower than the vapour pressure predicted by Raoult's law, the deviation is known as negative deviation.
The reason for the deviation is molecular interactions,A − B < A − A , B − B
Here, A is the solute and B is the solvent so, A-B shows the interaction between solute and solvent.
(b) The number of moles of glucose
=
= 0.056 mol
Molality of solution =
= 0.62 m
If the density of the solution is1.2 gmL − 1 100 g
= 83.3 mL
= 83.33 × 10 − 3 L
Molarity of solution =
= 0.67 M
(ii) Molal elevation constant
(b) Given; Mass of urea,
Molar mass of urea,
The solution of urea in water is isotonic to that of glucose solution.
OR
(a) According to Raoult's law, the partial pressure of a component is the product of vapour pressure of pure solvent and mole fraction of that component. When a solution shows deviation from Raoult's law over the complete range of concentration, the solution is known as a non-ideal solution.
The vapour pressure of the non-ideal solution can be higher or lower than the vapour pressure predicted by Raoult's law.
If the vapour pressure of the non-ideal solution is higher than the vapour pressure predicted by Raoult's law, the deviation is known as positive deviation.
If the vapour pressure of the non-ideal solution is lower than the vapour pressure predicted by Raoult's law, the deviation is known as negative deviation.
The reason for the deviation is molecular interactions,
Here, A is the solute and B is the solvent so, A-B shows the interaction between solute and solvent.
(b) The number of moles of glucose
If the density of the solution is
© examsnet.com
Go to Question: