CC2D2 Core Practical - Investigating Inks

Question 1

Describe how to separate soluble coloured substances

Answer 1

Chromatography:
Place a spot of the sample on a pencil line on a piece of chromatographt paper. Place the paper in a beaker of solvent (below pencil line)

Remove from solvent and leave to dry once solvent has travelled up 2/3 of the paper

Question 2

Why should the line be drawn onto chromatography paper in pencil

Answer 2

Pencil doesnt travel up the paper whereas pen ink would
Pencil is insoluble in the solvent

Question 3

Ink spots are placed above the level of the solvent in the beaker. Why?

Answer 3

If they were below the solvent level the ink would dissolve in the solvent rather than moving up the chromatography paper

Question 4

What is meant by a ‘solvent front’

Answer 4

The solvent front is the furthest distance reached by the solvent

Question 5

How can you use chromatography to see if a certain substance is present in a mixture

Answer 5

Run a pure sample of this substance alongside the unknown mixture
If the Rf value of the pure substance matches the value of one of the spots from the mixture, it is likely to be present

Question 6

Why should chromatography paper be removed from the solvent before the solvent front reaches the top

Answer 6

To allow the distance moved by the solvent to be measure so that the Rf value can be calculated

Question 7

What are the 2 phases in chromatography

Answer 7

Mobile phase - Solvent which carries substances up the stationary phase
Stationary phase - Paper or thin layer of an inert substance on a glass plate

Question 8

How do you calculate the Rf value

Answer 8

Rf = Distance travelled by substance
——————————————
Distance travelled by solvent

Rf is between 0 and 1

Question 9

In paper chromatography what is the stationary phase

Answer 9

The chromatography paper

Question 10

In paper chromatography what is the mobile phase

Answer 10

The solvent
e.g water or ethanol

Question 11

Describe how to obtain a sample of pure water from ink

Answer 11

Simple distillation: Gently heat the ink in a round bottomed flask using a Bunsesn burner. The water from the ink evaporates then cools in the condenser. The pure water is collected in a beaker

Question 12

How do you set up a condenser for simple distillation

Answer 12

Condenser should be horizontal water in at the bottom and water out of at the top

Question 13

When using simple distillation to collect pure water, what temperature will be on the thermometer

Answer 13

100ºC

Question 14

List precautions to take when using a Bunsen burner

Answer 14

Dont leave unattended
Turn off gas or leave on orange safety flame when not in use
Tie back long hair
Work in a clear space
Move any flammable substances away

Question 15

List precautions to take when handling harmful solvents

Answer 15

Wear gloves and safety goggles
Use in a well ventilated lab or use a fume cupboard
Clean up any spillages

Question 16

How could you separate salt from a mixture of salt and sand

Answer 16

Salt is soluble in water and sand isnt
Add water to the mixture
Filter the solution to remove the insoluble sand
Evaporate the water to collect the salt crystals