Chromatography and water

What is paper chromatography used for?

Separating soluble substances in a mixture.

What is the mobile phase in chromatography?

The solvent moving through the paper.

What is the stationary phase?

The chromatography paper.

Why do substances move different distances in chromatography?

They have different solubilities and attractions to the paper.

How can chromatography distinguish pure and impure substances?

Pure gives one spot; impure gives multiple spots.

How can chromatography identify an unknown substance?

Compare its spot with known substances.

What is the Rf equation?

Rf = distance travelled by substance ÷ distance travelled by solvent.

What range should an Rf value normally fall within?

Between 0 and 1.

Why is the starting line drawn in pencil?

Pencil does not dissolve in the solvent.

Why should the solvent front be marked quickly?

The solvent can evaporate.

What is the purpose of the ink core practical?

To investigate ink composition using distillation and chromatography.

How is ink separated using chromatography?

A solvent carries the ink components different distances up the paper.

How is groundwater made potable?

Through sedimentation, filtration and chlorination.

Why is sedimentation used in water treatment?

To allow larger suspended particles to settle.

Why is filtration used in water treatment?

To remove insoluble suspended particles.

Why is chlorine added to water?

To kill harmful microorganisms.

How can seawater be made potable?

By distillation to remove dissolved salts.

Why can’t filtration remove dissolved salts?

Dissolved salts pass through the filter.

Why must analytical water contain no dissolved substances?

Dissolved substances could interfere with analysis.