Thin layer chromatography (TLC) - WM

Question 1

What is chromatography

Answer 1

it is used to separate and/or identify the different compounds present in a mixture. It can also be used to purify an organic compound.

Question 2

What do all types of chromatography have

Answer 2

a stationary phase and a mobile phase

Question 3

For TLC what is the stationary phase and the mobile phase

Answer 3

S - thin layer of silica spread on a plastic sheet
M - the solvent moving up the plate

Question 4

How to do thin layer chromatography (TLC)

Answer 4

1. draw a pencil line at the botton of the TLC /paper
2. dissolve your test mixture and any reference compounds speratly in a small mount of solvent and spot them in different marked places on the line
3. stand the plat ein a beaker containing a small amount of chromatography solvent bwloe the pencil line
4. cover with a lid
5. allow the solvent to travle up the plate and when it gets near the top remvoe the plat enad mark the solvent front
6. allow to dry
7. locate spots
8. identify substances

Question 5

How to locate the spots on a TLC plate if they are colourless

Answer 5

viewing under a uv light, place the sheet in a beaker with a few crystals of iodine, spray the plate with a suitable locating agent

Question 6

How to tell if your sample is pure in TLC

Answer 6

if it only has one spot it is pure but if it has multiple then it is a mixture (TLC don’t tell how much of impurity)

Question 7

How to identify substances in TLC

Answer 7

match the heights reached with the heights of the reference spots or use Rf values

Question 8

Rf value equation

Answer 8

distance spot travelled/distance solvent front travelled