C12 Chromatography

Question 1

What is the mobile phase?
What is the stationary phase?
Distance travelled depends on…

Answer 1

Mobile phase carries different compounds in the sample (Mobile phase is the solvent)
Stationary phase is the paper
Distance travelled depends on solubility of a compound and how attracted it is to the stationary phase

(The more strongly attracted to mobile phase the further up the paper)

Question 2

How do you identify unknown compounds?

Answer 2

To identify unkown compounds, calculate Rf value. (Retention factor) which we can then compare to known values in database

Question 3

Explain how to chromatography

Answer 3

Steps:
Draw pencil line 1cm from bottom, then draw spots along the line.
Hang paper in solvent ensuring solvent is not higher then pencil line.

Take paper out when solvent is nearly at top and mark how far the solvent travelled
Let paper dry, then measure to calculate Rf Value
There is also a lid involved… ;)

Question 4

Testing for gases:
Hydrogen?

Answer 4

Hydrigen: Hold lit splint near open end of test tube, positive test will event in hydrogen burning, rapidly with a squeaky pop.

Question 5

Oxygen

Answer 5

Oxygen: Hold a glowing splint in sample of gas, positive test - glowing splint will relight

Question 6

Carbon dioxide

Answer 6

Carbon dioxideL Bubble gas through limewster (aqueous calcium hydroxide) Positive - Limewater turns cloudy

Question 7

Chlorine

Answer 7

CHlorine: Use damp blue litmus paper, positive result will bleach it white.

Question 8

Explain reasons for certain steps in chromatography

Answer 8

Bassline drawn in pencil to prevent ink running.
Baseline must be above surface of solvent otherwise samples will disolve.
Lid stops solvent evaporating

Question 9

Chromatography is used to…?

Answer 9

Chromatography is used to seperate a mixture of substances that can be dissolved in the same solvent

Question 10

Number of dots

Answer 10

A sample with one dot shows that it is pure/
A mixture contains multiple dots

Question 11

Rf calculation

Answer 11

Rf value: DIstance travelled by compound / distance travelled by solvent (mobile phase).

Question 12

Chromatography identifies

Answer 12

Used to identify unknown compounds in a sample that can be dissolved in the same solvent

Chromatography is used to seperate and identify unknown compounds i

Question 13

Catalysts

Answer 13

A catalyst is a chemical added to a reaction which increases the rate.