Chromatography What is the main purpose of the mobile phase in chromatography? I

Question

Chromatography

What is the main purpose of the mobile phase in chromatography? It transports substances across the stationary phase leading to separation of components based on affinities for the stationary or mobile phase As it evaporates, the increasing vapor pressure causes substances in a mixture to separate It exposes components of substances on different areas of the stationary phase by chemical reaction with the components It creates an excess of protons so that negatively charged parts of a mixture will be pulled away from other components A mixture is composed of both compound A and compound B. Compound A is significantly polar while compound B is non polar. If a non polar mobile phase and a polar stationary phase are used to separate the two compounds, which compound (A or B) will travel further from the origin? They will travel the same distance Compound B Compound A It depends on many factors including Einstein's Theory of Relativity Chromatography is used to separate a mixture. One spot is observed 5.2 cm from the origin. The solvent front traveled 10.1 cm from the origin. The origin is 1.0 cm from the base of the chromatogram. What is the retention factor for the spot? 0.51 1.94 0.57 0.46

Explanation / Answer

Solution :-

1)Chromatography is the technique uses the attraction of the components with the mobile phase and stationary phase to separate the components.

Purpose of the mobile phase

It transports substances across the stationary phase leading to separation of components based on the affinities for the stationary or mobile phase

2) A is polar and B is non polar

Mobile phase is non polar and stationary phase is polar

Therefore the non polar compound B will move with the non polar mobile phase and polar compound A will stick to the stationary phase which is polar therefore

Compound B will travel further from the origin.

3) Retention factor (Rf) = distance traveled by component spot / distance traveled by the solvent

Distance traveled by solvent = 10.1 cm – 1.0 cm = 9.1 cm

Lets put the values in the formula

Rf = 5.2 cm/9.1 cm

     = 0.57

Therefore the option ‘C’ is the correct answer.

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