Ch-3: Seperation techniques

Question 1

What is filtration?

Answer 1

Filtration is a seperation technique used to separate an undissolved solid from a mixture of the solid and a liquid

Question 2

Describe the process of Filtration

Answer 2

1. Filter paper is placed in a filter funnel above another beaker
2. The mixture of insoluble solid and liquid is poured into the filter funnel
3. Filter paper will only allow small liquid particles to pass through as the filtrate
4. Solid particles are too large to pass through the filter paper so it will stay behind as a residue

Question 3

There is a mixture of solid iodine, sand and salt. Make a plan to seperate all 3 from this solid mixture.

Answer 3

1. Heat the solid iodine, it will sublime and get seperated from the mixture
2. Add water to the remaining solid mixture. The salt will dissolve but the sand will not.
3. Pour the mixture through a filter paper.
4. The salt will pass through as filtrate but sand will get stuck on the filter paper as residue.

Question 4

What is simple distillation?

Answer 4

Used to separate a liquid and soluble solid from a solution depending on boiling point difference

Question 5

Describe the process of simple distillation

Mixture: salt water / sea water

Answer 5

1. The mixture (salt water) is kept in a round bottom flask
2. We then heat up the mixture
3. On heating, once the mixture reaches 100 degree celcius, water will start to boil
4. The water vapour will rise and enter the condenser, turning it into liquid that is collected in the receiver beaker
5. After all the water evaporates, all thats left in the round bottom flask is the solid salt

Question 6

What is fractional distillation?

Answer 6

Fractional distillation is a seperation process used to separate two or more liquids that are miscible with one another depending on their boiling point difference

Question 7

Function of:

Fractionating coloumn

Answer 7

To seperate the mixture depending on their boiling point difference. lower boiling power distills over first

Question 8

Function of:

Condenser

Answer 8

To turn gas into liquid and deliver distillate into the receiver beaker

Question 9

Function of:

Receiver beaker

Answer 9

Must be kept open so that if any gaseous particle present, they can escape. Is used to collect distillate seperately

Question 10

What is paper chromatography?

Answer 10

Paper chromatography is a seperation technique used to separate substances that have different solubilities in a given solvent

Question 11

What is the pencil line drawn on the chromatography paper called?

Answer 11

Base line

The line on which a spot of the sample is dropped

Question 12

How does the solvent travel up the paper?

Answer 12

The solvent travels up the paper by capillary action taking the sample with it

Question 13

Which substance travels the longest distance?

Higher or Lower solubility?

Answer 13

The substance with the higher solubility travels the longest distance

Question 14

True/False:

Different spots on the chromatography paper show same components present in the sample

Answer 14

False, Different spots on the chromatography paper show different components present in the sample

Question 15

True/False:

Base line should not be dipped into the water

Answer 15

True, the chromatography paper should be touching the water but not up to the base line

Question 16

True/False:

Different substances (sample) travel same distance with same rate

Answer 16

False, Different substances (sample) travel different distance with different rate

Question 17

What is the Rf value formula?

Answer 17

• Rf =

Distance travelled by sample
—————————————-
Distance travelled by solvent

Question 18

If one of the chemicals in a paper chromatogram does not show any spot, what would you do to further identify the chemical?

Answer 18

I would spray locating agent, but if its still not visible, i would change the solvent

Question 19

What is seperating funnel?

Answer 19

Seperating funnel can be used to seperate immiscible liquid mixture depending on their density difference. More dense liquid will be collected first

Ex: the mixture of water and oil can be seperated by seperating funnel

Question 20

State two physical properties for whih we can do fractional distillation

Answer 20

1. boiling point
2. miscibility