3️⃣ PAG 3: separation techniques

Question 1

SAFETY

Answer 1

• Leaf extract – HIGHLY FLAMMABLE AND IRRITANT
• Propanone – HIGHLY FLAMMABLE AND IRRITANT
• wear eye protection
• Capillary tubes can be fragile and care should be taken so they do not break.

(This is when separating chlorophyll - so different )

Question 2

Method -

Answer 2

Method

draw a pencil line across the chromatography paper, 1-2 cm from the bottom
use a pipette or capillary tube to add small spots of each ink to the line on the paper
place the paper into a container with a suitable solvent in the bottom
allow the solvent to move through the paper, but remove the chromatogram before the solvent reaches the top
mark the level that the solvent reached using a pencil so that you can measure the distance travelled by the solvent when it dries
allow the chromatogram to dry, then measure the distance travelled by each spot and by the solvent

Question 3

What is capillary tube

Answer 3

Glass tubing which is very narrow inside.

Question 4

What is chromatogram

Answer 4

The results of separating mixtures by chromatography.

Question 5

Results recorded in a suitable table - what are the columns

Answer 5

Ink, spot colour, distance travelled by spot

Question 6

Analysis —

Answer 6

1. Calculate the Rf value of each spot:

Rf = Distance traveled by substance / distance travelled by solvent

2. Compare the Rf values and colours of each spot in the inks. Describe their similarities and differences.

Question 7

Explain why the distances travelled by each spot were measured in millimetres (mm), rather than in centimetres (cm).

Answer 7

Measurements in mm are more precise than those in cm. They will give more precise Rf values.

Question 8

Hazards, risks and precautions (2)

Answer 8

Harmful solvent Skin irritation Avoid skin contact, eg wear gloves

Harmful solvent Breathing difficulties Ensure adequate ventilation or use a fume cupboard