Chromatography Lesson Note International GCSE.pptx

Unit-1, Lesson-2, Mixtures separation methods; Chromatography Lesson International GCSE Chemistry PPT

1. Chromatography

2. The elephant and mouse proverb... Interpretation of Chromatography... Which is able to run more quickly through the forest?

3. A mixture of substances can be separated by paper chromatography such as ink; the mixture of different colored dye. Note: Pure substance cannot be separated.

4. Pure substances will produce only  one spot  on the chromatogram If two or more substances are the same, they will produce identical chromatograms If the substance is a  mixture , it will separate on the paper to show all the  different   components  as  separate  spots An impure substance therefore will produce a chromatogram with more than one spot

5. Why do we use paper chromatography?

6. How chromatography works?

7. Rf Values……… These values are used to  identify  the components of mixtures The  R f  value of a particular compound is always the  same  but it is dependent, however, on the solvent used If the solvent is changed then the value changes Calculating the  R f   value allows chemists to  identify unknown substances  because it can be compared with  R f   values of known substances under the same conditions These values are known as  reference values

8. Calculating Retention factor ( Rf ) values How much a substance is held back by the paper is called the Retention factor ( Rf ) Value. You can calculate this by:

9. Reminder….. The Rf value will always lie between 0 and 1; the closer it is to 1, the more soluble is that component in the solvent The  R f  value is a ratio and therefore has no units