Question

What is the relationship between IMFs and paper chromatography? Please explain (I don’t understand this concept!)

Answer 1

CChromatography is a technique used to separate the components of a mixture. The mixture is mounted on a support called stationary phase. For example in paper chromatography paper is used as stationary phase. The mixture in mounted at about 1cm above the bottom of stationary phase. After mounting the mixture on stationary phase the stationary phase is put in a solvent. This solvent is called the mobile phase. Minimum solvent should be used so that the solvent shoul not touch the mixture. The mobile phase move up the stationary phase by capillary action. While moving upwards the components of mixture are also dragged upward. But the components of mixture move with differnt speeds. As a result these get separated. The different speeds of the components is because of different forces of attraction between the components and stationary phase.

In chromatography the main role is of the intermolecular forces of attraction as it depends on the forces of attraction with which a organic compound is adsorbed by the solvent . In chromatography paper is prepared by applying silica coating on the paper as silica is best adsorbent of almost all the organiv compounds. Mobile phase is the particular solution in whuch the chromatographic paper is dipped and allowed to run on the basis of adsorbance of the unknown organic compounds. Dye stuffs are the compounds which we have to separate by chromatography method.

Dye stuffs are separated to different degrees by different solvents in mobile phase due to the presence of different compound present in the dye stuff according to their respective adsorbing power and rf value.

A solid phase or a stationary phase has a very great influence om the separation as it holds the dye stuff according to their adsorbance value .

Characteristics that make a good chromatography solvwnt

1. Good adsorbent

2. Solubility

3. should not dissolve the organic compound to make a new compound.

Paper Chromatography:

In chromatography there are two types of phases : mobile and stationary.

A mixture of substances are applied on stationar phase (paper).

Moving phase is solvent which contains mixture of solutes.

Position of a solute in chromatogram is given by Rf factor.

Rf factor is the ratio of distance travelled by solute to the distance travelled by solvent.

Different solutes have different intermolecular forces of attraction with moving and stationary phase.

Solutes which have higher intermolecular force of attraction with stationary phase moves slower and thus have lower Rf value than the solute which have smaller intermolecular force of attraction with stationary phase.