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Chapter 36
125
Chapter 36 Separation of Mixtures A.
Multiple Choice Questions
1. 2. 3. 4. 5.
C. A. A. D. B.
6.
D.
7.
A.
B. 1. 2. 3. 4.
Paper chromatography (1) and (2) only (2) only Filtration Add the mixture to water and then carry out filtration Crystallization, filtration, fractional distillation (1) only
(b)
Fill in the Blanks Impurities filtrate, residue fractional distillation, anti-bumping granules “Quickfit” (c)
C. 1.
Comprehensive Questions 1. 2.
The solubility of the solute in the solvent The adsorption of the solute on the chromatography paper
2.
Saturated solution is a solution in which a solvent has dissolved the maximum mass of a solute at a specified temperature.
3.
Temperature, humidity and ventilation.
4.
(a)
(i)
(ii)
To separate substances in the same state (e.g. solid/solid, liquid/liquid and gas/gas) and to identify these substances. Since different substances have different solubilities in the solvent and different extent of adsorption on the
(d)
chromatography paper, they would be carried upwards by the solvent at different speeds. Hence, different solutes (or components in a sample) can be separated. (iii) Separation of dyes in black ink (i) To separate solutes as crystals from a solution. (ii) Crystallization occurs only when the solution is saturated. If the solution provided is unsaturated, we can either evaporate part of the solvent in the solution or lower its temperature to prepare a saturated solution. (iii) Crystallization of copper(II) sulphate by cooling (i) To separate a solid from a liquid. (ii) In filtration, the mixture of liquid and solid is poured into a filter funnel with a piece of folded filter paper. Usually, a glass rod is used to guide the flow. After filtration, the residue is washed with a small amount of cold distilled water to remove any soluble impurities on the surface of the residue. The cleaned solids are then removed for drying. The liquid collected is called filtrate. (iii) Obtaining copper(II) sulphate crystals from its saturated solution (i) To separate a non-volatile solid from a liquid mixture. (e.g. separate a solute from a Chapter 36 Solutions (EE).doc
126
Part 9
solution). When all the solvents in the solution change to vapour in air, the solute is left behind as a solid. (iii) Evaporation of sodium chloride solution in order to obtain sodium chloride solid (i) To separate a solvent from a solution containing non-volatile solutes. (ii) On heating, a solution boils to produce a vapour of solvent (e.g. steam from aqueous solution.) When the vapour comes to a cold surface, it condenses on it as distillate. (iii) Distillation of the aqueous solution of sodium chloride in order to obtain pure water (i) To separate a mixture of two or more miscible liquids. (ii) On heating, a mixture boils to produce a vapour composed of different components. When fractional distillation is carried out using “Quickfit” apparatus, the vapour rises up in the fractionating column. (iii) Fractional distillation of petroleum (ii)
(e)
(f)
(e)
spots which will mislead the results. No. The colourings of chocolate beans on the crosses dissolve in the solvent and thus they cannot move upwards.
7.
The more sufficient the time for solute particles to arrange themselves regularly in crystals, the larger the crystal will be formed. Time for crystallization in descending order: (a) > (c) > (d) > (e) > (b) Thus, the size of crystals obtained in descending order: (a) > (c) > (d) > (e) > (b)
8.
(a)
1. 2. 3.
OR 1.
2. 3. (b)
1.
5.
HKCEE Question
2.
6.
(a) (b) (c)
3.
(d)
B 6 (i)
Some colourings have the same relative solubilities in the water (mobile phase) and in the water film on the paper. (ii) Perform paper chromatography again using another solvent as eluent. No. The ink in pen can dissolve in the rising solvent / eluent and then move up the paper to give additional
Chapter 36 Solutions (EE).doc
9.
Carry out crystallization to obtain sugar crystals. Filter the mixture to collect the crystals. Carry out fractional distillation to separate ethanol and water. Carry out fractional distillation to separate ethanol from aqueous solution of sugar. Carry out crystallization to obtain sugar crystals. Filter the mixture to collect the crystals. Carry out crystallization to obtain sugar crystals. Filter the mixture to collect the crystals. Carry out fractional distillation to separate ethanol from aqueous solution of ethyl ethanoate.
(a) Since calcium carbonate is insoluble in water while calcium chloride is soluble in water, we can dissolve the mixture in water. Then, filter the solid to obtain calcium carbonate. Carry out crystallization of the remaining
Chapter 36
solution by evaporation, and then filtration in order to obtain pure calcium chloride. (b)
D. 1.
Essay-type Question Guideline to the essay:
Crystallization 1. To separate the solutes as crystals from a solution. 2. Crystallization occurs only when the solution is saturated. If the Characteristics solution provided is unsaturated, we can either evaporate the solvent in the solution or lower its temperature to prepare a saturated solution.
Examples
10. Add water to the mixture, X and Z dissolve while Y remains in solid state. Carry out filtration to obtain solid Y. Use separating funnel to extract the remaining solution containing X and Z with volasil. The aqueous layer contains X while the organic layer contains Z.
127
Crystallization of copper(II) sulphate by cooling
Distillation 1. To separate a solvent from a solution containing non-volatile solutes. 2. On heating, a solution boils to produce a vapour of solvent (e.g. steam from aqueous solution When the vapour comes to a cold surface, it condenses on it as distillate.
Evaporation 1. To separate a non-volatile solid from a liquid mixture (e.g. separate a solute from a solution). 2. When all the solvents in the solution change to vapour in air, the solute is left behind as a solid.
Distillation of the aqueous solution of sodium chloride
Evaporation of sodium chloride solution
Chapter 36 Solutions (EE).doc
125
Chapter 36 Separation of Mixtures A.
Multiple Choice Questions
1. 2. 3. 4. 5.
C. A. A. D. B.
6.
D.
7.
A.
B. 1. 2. 3. 4.
Paper chromatography (1) and (2) only (2) only Filtration Add the mixture to water and then carry out filtration Crystallization, filtration, fractional distillation (1) only
(b)
Fill in the Blanks Impurities filtrate, residue fractional distillation, anti-bumping granules “Quickfit” (c)
C. 1.
Comprehensive Questions 1. 2.
The solubility of the solute in the solvent The adsorption of the solute on the chromatography paper
2.
Saturated solution is a solution in which a solvent has dissolved the maximum mass of a solute at a specified temperature.
3.
Temperature, humidity and ventilation.
4.
(a)
(i)
(ii)
To separate substances in the same state (e.g. solid/solid, liquid/liquid and gas/gas) and to identify these substances. Since different substances have different solubilities in the solvent and different extent of adsorption on the
(d)
chromatography paper, they would be carried upwards by the solvent at different speeds. Hence, different solutes (or components in a sample) can be separated. (iii) Separation of dyes in black ink (i) To separate solutes as crystals from a solution. (ii) Crystallization occurs only when the solution is saturated. If the solution provided is unsaturated, we can either evaporate part of the solvent in the solution or lower its temperature to prepare a saturated solution. (iii) Crystallization of copper(II) sulphate by cooling (i) To separate a solid from a liquid. (ii) In filtration, the mixture of liquid and solid is poured into a filter funnel with a piece of folded filter paper. Usually, a glass rod is used to guide the flow. After filtration, the residue is washed with a small amount of cold distilled water to remove any soluble impurities on the surface of the residue. The cleaned solids are then removed for drying. The liquid collected is called filtrate. (iii) Obtaining copper(II) sulphate crystals from its saturated solution (i) To separate a non-volatile solid from a liquid mixture. (e.g. separate a solute from a Chapter 36 Solutions (EE).doc
126
Part 9
solution). When all the solvents in the solution change to vapour in air, the solute is left behind as a solid. (iii) Evaporation of sodium chloride solution in order to obtain sodium chloride solid (i) To separate a solvent from a solution containing non-volatile solutes. (ii) On heating, a solution boils to produce a vapour of solvent (e.g. steam from aqueous solution.) When the vapour comes to a cold surface, it condenses on it as distillate. (iii) Distillation of the aqueous solution of sodium chloride in order to obtain pure water (i) To separate a mixture of two or more miscible liquids. (ii) On heating, a mixture boils to produce a vapour composed of different components. When fractional distillation is carried out using “Quickfit” apparatus, the vapour rises up in the fractionating column. (iii) Fractional distillation of petroleum (ii)
(e)
(f)
(e)
spots which will mislead the results. No. The colourings of chocolate beans on the crosses dissolve in the solvent and thus they cannot move upwards.
7.
The more sufficient the time for solute particles to arrange themselves regularly in crystals, the larger the crystal will be formed. Time for crystallization in descending order: (a) > (c) > (d) > (e) > (b) Thus, the size of crystals obtained in descending order: (a) > (c) > (d) > (e) > (b)
8.
(a)
1. 2. 3.
OR 1.
2. 3. (b)
1.
5.
HKCEE Question
2.
6.
(a) (b) (c)
3.
(d)
B 6 (i)
Some colourings have the same relative solubilities in the water (mobile phase) and in the water film on the paper. (ii) Perform paper chromatography again using another solvent as eluent. No. The ink in pen can dissolve in the rising solvent / eluent and then move up the paper to give additional
Chapter 36 Solutions (EE).doc
9.
Carry out crystallization to obtain sugar crystals. Filter the mixture to collect the crystals. Carry out fractional distillation to separate ethanol and water. Carry out fractional distillation to separate ethanol from aqueous solution of sugar. Carry out crystallization to obtain sugar crystals. Filter the mixture to collect the crystals. Carry out crystallization to obtain sugar crystals. Filter the mixture to collect the crystals. Carry out fractional distillation to separate ethanol from aqueous solution of ethyl ethanoate.
(a) Since calcium carbonate is insoluble in water while calcium chloride is soluble in water, we can dissolve the mixture in water. Then, filter the solid to obtain calcium carbonate. Carry out crystallization of the remaining
Chapter 36
solution by evaporation, and then filtration in order to obtain pure calcium chloride. (b)
D. 1.
Essay-type Question Guideline to the essay:
Crystallization 1. To separate the solutes as crystals from a solution. 2. Crystallization occurs only when the solution is saturated. If the Characteristics solution provided is unsaturated, we can either evaporate the solvent in the solution or lower its temperature to prepare a saturated solution.
Examples
10. Add water to the mixture, X and Z dissolve while Y remains in solid state. Carry out filtration to obtain solid Y. Use separating funnel to extract the remaining solution containing X and Z with volasil. The aqueous layer contains X while the organic layer contains Z.
127
Crystallization of copper(II) sulphate by cooling
Distillation 1. To separate a solvent from a solution containing non-volatile solutes. 2. On heating, a solution boils to produce a vapour of solvent (e.g. steam from aqueous solution When the vapour comes to a cold surface, it condenses on it as distillate.
Evaporation 1. To separate a non-volatile solid from a liquid mixture (e.g. separate a solute from a solution). 2. When all the solvents in the solution change to vapour in air, the solute is left behind as a solid.
Distillation of the aqueous solution of sodium chloride
Evaporation of sodium chloride solution
Chapter 36 Solutions (EE).doc
