Lab 3B

Separation of a Mixture by Paper ChromatographyChromatography is one technique used by chemists to separate mixture of chemical compounds in order to identify or iso;ate their components on chromatography, mixture are separated according to the different solubilities of the components in liquids, or their adsorption on solids.
The method of identifying components is to calculate the Rf value of each.
Rf=d1/d2 where d1=distance traveled by solute
d2=distance traveled by solvent
the lab report:
Objective: 1. To assemble and operate a paper chromatography apparatus
2. To study the meaning and significance of Rf values
3. To test various food colourings and to calculate their Rf values
4. To compare measured Rf values with standard Rf values
5. To separate mixtures of food colourings into their components
6. To identify the components of mixture by means of their Rf values

Material and Equipment:Refer to page 33 in Health Lab Text, Lab 3B
Procedure:
Refer to page 33 in Health Lab Text, Lab 3B

Data and Observation:Attached to the back of the lab report.(on the paper....)

Analysis of Results:1. A, We tested the yellow colouring. It contains Yellow #6
B. We didn't get any.
2. Green food colouring contains about 1/3 of yellow colouring(Yellow #6) and 2/3 of blue colouring(Blue #2).
3. The unknown mixture is composed of 1/2 of red colouring(Red #4), 1/3 of blue colouring(Blue #2) and 1/6 of Yellow colouring(Yellow #6)
4. The ink mark might be blurred and move up.
5. The green colouring can be decomposed into blue and yellow, but red, yellow and blue colourings cannot be decomposed.

Following-Up Questions1. The Rf of those colourings are 0.78 and 0.38. They are likely to be Red#3 and Yellow #6.
2. d1= 12*1.0 = 12 d2 = 12*0.41 = 4.92 Δd = 12-4.92 = 7.08cm
3. There is no way that a solute move above the solvent. It is impossible.

ConclusionFrom this lab, we got to know the way we separate a mixture by Paper Chromatography. The Rf value means the ratio of distances raveled by solute and solvent. Different substances usually have different Rf values. We can use this property to separate different substances. And we can also identify the substances by checking the table of Rf values.