Experimental techniques and chemical analysis

Question 1

chromatography

Answer 1

a method of separation of mixtures of dissolved substances

Question 1

crystallisation

Answer 1

the process of forming crystals from a liquid

Question 2

filtrate

Answer 2

a liquid or solution that has passed through a filter paper

Question 3

filtration

Answer 3

the process of separating a solid from a liquid using a filter paper which does not allow the solid to pass through

Question 4

fractional distillation

Answer 4

a method of separation of a mixture of liquids with different boiling points

Question 5

saturated solution

Answer 5

a solution containing the maximum concentration of a solute dissolved in the solvent as a specified temperature

Question 6

residue

Answer 6

a substance that remains after evaporation , distillation or any similar process

Question 7

(simple) distillation

Answer 7

the process of using evaporation and condensation to form a pure liquid from a solution

Question 8

solute

Answer 8

a substance that is dissolved in a solvent

Question 9

solution

Answer 9

a mixture of one or more solutes dissolved in a solvent

Question 10

solvent

Answer 10

a substance that dissolved a solute to form a solution

Question 11

substance

Answer 11

a general term that refers to elements, mixtures and compounds.

Question 12

example of when simple distillation could be used

Answer 12

to seperate pure water from a solution of sodium chloride

Question 13

apparatus needed for simple distillation

Answer 13

1. thermometer
2. distillation flask
3. condenser
4. beaker

Question 14

steps of simple distillation of NaCl

Answer 14

1. flask is heated
2. water in the NaCl evaporates and water vapour enters the condenser as water
3. the water drips out of the condenser and collects in the beaker
4. the water is pure and is referred to as distilled water
5. Nacl does not vaporise or melt because it has a very high melting point, therefore it remains in the distillation flask

Question 15

uses of fractional distillation in the laboratory

Answer 15

ethanol and water

Question 16

apparatus needed in fractional distillation

Answer 16

1. thermometer
   2.condenser
2. fractionating column
3. distillation flask
4. conical flask

Question 17

steps of the fractional distillation of ethanol and water

Answer 17

1. ethanol has a boiling point of 78C and water has a boiling point of 100C
2. the flask is heated and ethanol vapour enters the fractionating column
   - some water also evaporates and enters the column as vapour
3. the water vapour condenses in the fractionating column and drips back down into the distillation flask
4. when the temperature reaches 78C the ethanol vapour reaches the tip of the fractionating column and enters the condenser.
5. liquid ethanol collects as the distillate and all water remains in the distillation flask

Question 18

apparatus needed for chromatography

Answer 18

1. chromatography paper
2. solvent
3. beaker

Question 19

steps of chromatography

Answer 19

1. spot of ink is placed on the chromatography paper
2. paper is placed in a suitable solvent in the beaker
3. as the solvent rises, the dyes in the ink seperate

Question 20

formula for Rf value

Answer 20

distance travelled by component / distance travelled by solvent

Question 21

ways to identify cations

Answer 21

1. aqueous sodium hydroxide
2. flame tests
3. aqueous ammonia