Biology: Practicals

Question 1

Chromatography Required Practical: How to calculate the Rf value?

Answer 1

Rf = distance travelled by the compound for the origin / distance traveled by the solvent from the origin

Question 2

Chromatography Required Practical:

Answer 2

1) Draw a line at the bottom of the piece of Chromatography paper with a pencil (this is called the origin)
2) Place a small amount of the sample onto the paper at the origin
3) Let it dry before adding a second drop
4) Repeat to build up the concentration
5) Place the paper into the solvent up to the origin line
6) Allow the solvent to run
7) Before the solvent reaches the top of the paper remove it from the solvent
8) Draw a line at the point where the solvent has reached (solvent front)
9) Allow the paper to dry

Question 3

Chromatography Required Practical: Identification

Answer 3

a) Comparing to known standards
b) Calculation of Rf values and comparison to Rf values in tables for the same solvent