PHASE EQUILIBRIUM WORKSHEET

1.Select the composition diagram that exhibits a mixture showing positive deviation from Raoult's law.

A

B

C

D

2.Select the correct statement for an ideal mixture of two liquids.

AIt is a solution obeying Boyle's law

BIt is a solution obeying Raoult's law

CThe solution making process is endothermic

DThe solution mixing process is exothermic

3.P and Q two miscible liquids forming an ideal solution. The vapour pressure of P is 48 kPa and vapour pressure of Q is 36 kPa at . Calculate the total vapour pressure at the same temperature of a mixture that contains 3 moles of P and 1 mol of Q.

A21 kPa

B36 kPa

C45 kPa

D84 kPa

4.Identify the liquid mixture that obeys Raoult's law.

AHexane and Heptane

BBenzene and Ethanol

CNitric acid and water

DPropanone and trichloromethane

5.The question below is based on the following information. Vapour pressure of cyclohexane and benzene at is 12 kPa and 10 kPa respectively. A mixture of cyclohexane and benzene forms an ideal solution. The mole fraction of cyclohexane in the mixture is 0.5.

Calculate the total vapour pressure of the solution in kPa.

A16

B14

C11

D10

6.The question below is based on the following information. Vapour pressure of cyclohexane and benzene at is 12 kPa and 10 kPa respectively. A mixture of cyclohexane and benzene forms an ideal solution. The mole fraction of cyclohexane in the mixture is 0.5.

Calculate the mole fraction of cyclohexane in the vapour that is in equilibrium with the solution.

A0.25

B0.55

C0.60

D0.65

7.The two following chromatograms were obtained by analysing one sample of a multiple-component mixture.

Identify the number of components from the above chromatograms.

A3

B4

C5

D6

8.An ideal solution is formed when 1 mol of liquid Q and 3 moles of liquid R are mixed. Consider that the vapour pressure of pure Q is x and of pure R is y. Calculate the total vapour of the solution.

A

B

C

D

9.__________is an analytical method used to separate solutes where separation is done by differential movement through a porous medium. The movement is caused by a flow of solvent.

ADiffusion

BFractional distillation

CChromatography

DSolvent extraction

10.Q an organic compound was distilled in steam at 101 kPa. Temperature at which distillation was carried out was was 72 kPa. 71.6% by mass of the distillate was found to be Q. Calculate the relative molecular mass of Q.

A156.90

B123.60

C112.06

D86

11.The following diagram represents the vapour pressure against composition curve of a mixture of hexane and heptane at temperature T.

On fractional distillation of 70% heptane and 30% hexane identify the composition of the first and the second distillate.

1st distillate2nd distillate

AHexane Heptane

BHeptaneHexane

CHeptaneHeptane + Hexane

DHexaneHexane + Heptane

12.A solution of 5.0 gm organic compound Q in 50 cm3 of H2O was shaken with 100 cm3 of ether. After separation, the aqueous solution was found to contain 0.98 gm of Q. Calculate the partition coefficient of Q between ether and water.

A0.381

B0.525

C2.625

D6.25

13.In column chromatoghraphy for the separation of substances in solution, absorbed solutes can be washed right through the column one at a time by a suitable solvent. Name the process.

AAbsorption

BAdsorption

CPolymerisation

DElution

14.The following diagram is the boiling pointcomposition of a mixture of two liquids P and Q.

What is the distillate composition when a mixture of composition Z is fractionally distilled?

APure P and azeotropic mixture

BPure P

CAzeotropic mixture

DPure Q and azeotropic mixture

15.A mixture of C6H5Br and steam at a pressure of 101 kPa and temperature was distilled. The resulting distillate had 100 g of H2O. Vapour pressure of H2O at is 85 kPa. Calculate the percentage by mass of C6H5Br in the distillate. (Relative molar mass: C6H5Br =156.5; H2O =18.0)

A100%

B76%

C62%

D50%

16.The following diagram shows a vapour pressure of a mixture of two liquids P and Q.

P and Q most likely

Apropan-l-ol and propan-2-ol

Bethanol and benzene

Cwater and nitric acid

Dhexane and heptane

17.Vapour pressure of hexane at is 54 kPa. What is the vapour pressure of hexane in an ideal mixture of 8.6 g hexane and 10 g of heptane at this temperature? [ Relative molar mass: hexane= 86, heptane= 100]

A38 kPa

B27 kPa

C11 kPa

D5.4 kPa

18.The following diagram is the boiling pointcomposition of a mixture of two liquids P and Q.

Identify the two liquids obtained when mixture X is separated by efficient fractional distillation.

AP and X

BQ and Y

CP and Y

DP and Q

SECTION B

19.

In paper chromatography the paper

1is marked with a spot of the solution to be analysed

2acts as an absorbent

3is filter paper of suitable quality.

20.

Identify the liquids that are completely miscible in all proportions at room temperature and a pressure of 1 atm.

1Water and benzene

2Phenylamine and water

3Water and propanone

21.

Identify the factors that affect the vapour pressure of a liquid.

1intermolecular forces

2temperature

3surface area of the liquid

22.

Identify the conditions under which the partition law does not work.

1when temperature changes

2when solutions are concentrated

3when the solute dissociates or associates with the solvent

23.

Identify the advantages of using ether as an extracting solvent.

1Can dissolve many organic compounds

2Is chemically inert

3Has a low boiling point

24.

Steam distillation can be used

1to separate miscible liquid mixtures

2for extraction and purification of organic compounds with high relative molecular masses

3to determine relative molecular masses of unknown organic compounds

25.

Boiling pointcomposition curves at constant pressure with a maximum value is obtained for mixtures comprising

1liquid oxygen and liquid nitrogen

2water and nitric acid

3water and hydrochloric acid

1.The following figure shows a partly completed boiling point against composition diagram at constant pressure for two miscible liquids A and B.

(a)Given the boiling point of pure A is and pure B is complete the diagram.

[4 marks]

(b)A liquid mixture consisting of 50% of A by mass is subjected to fractional distillation. Find out

(i)The boiling point of the mixture

[2 marks]

(ii)The composition of the vapour in equilibrium with the liquid mixture at its boiling point.

[2 marks]

(c)Sketch the vapour pressure against composition diagram expected to be obtained at constant temperature for mixture A and B.

[2 marks]

2.Raoult Law is based on the fact that a simple relationship exists between the relative lowering of vapour pressure and the concentration of an ideal solution expressed as mole fraction of solute.

(a)What do you mean by 'mole fraction' of a solute?

[4 marks]

(b)Name two liquid which form approximately ideal mixtures over a whole composition.

[2 marks]

(c)On the axes below, draw and label the boiling point composition curves for mixtures of the two liquids given in (b). Show both liquid and vapour composition in the diagram.

[4 marks]

3.(a)Why is ethoxyethane particularly suitable for the extraction of an organic compound from an aqueous layer?

[7 marks]

(b)An aqueous solution of butanedioic acid, HOOCC2CH2COOH was shaken with ethoxyethane at until equlibrium was attained. of the aqueous layer required NaOH(aq) and of ethoxyethane layer required aqueous sodium hydroxide for neutralisation. Calculate the partition coefficient at .

[9 marks]

4.An organic compound X is four times as soluble in ether as in water.

(a)Express this in terms of partition coefficient.

[6 marks]

(b)10 g compound X dissolved in 100 cm3 of water is extracted with 100 cm3 of ether. What mass of compound X is extracted into ether?

[9 marks]

(c)Calculate the total mass of the compound that would have been extracted by successively using two 50 cm3 portions of solvents.

[9 marks]

Answer 1C19D

2B20A

3C21B

4B22D

5C23D

6B24B

7A25C

8B

9C

10C

11A

12C

13D

14C

15C

16.C

17.B

18B

PAPER 2

PHASE EQUILIBRIUM

Q1 (a)

(b)(i) boiling point of mixture (ii) 30% of A by mass and 70% of B by mass.

(c)

Q2 (a) The mole fraction of a solute is the number of moles of that solute divided by the total number of moles present.

where n = no of moles.

(b) Heptane and hexane forms an ideal mixture.

(c)

3 (a) Ethoxyethane is a suitable extracting solvent because it is almost immisicible in water (floats) and can be easily separated from water. it has a low boiling point and can be distilled from the extracted solution using a water bath, leaving behind the organic compound. many organic compounds are completely soluble in ethoxyethane. It is chemically inert and does not react with many organic compounds.

(b)

2. (a) Partition coefficient

(b)Let mass of X extracted by ether = a gThus, mass of X remaining in water = (10-a) g

or

(b) First extraction:Let mass of X extracted by ether = Thus, mass of X remaining in water or

Second extraction:Mass of solute X remaining in the aqueous layer Let mass of X extracted by ether Thus, mass of X remaining in water

10