Paper Chromatography and Separating immiscible liquids E Haniff

Paper Chromatography and Separating immiscible liquids E. Haniff

Objectives • Separate a mixture of different solutions using a given solvent (by difference of solubilities) • Separate a mixture of immiscible liquids

What are immiscible liquids? • Immiscible liquids are two liquids which cannot be dissolved in one another • They form two distinct layers

Separating immiscible liquids

Title: Separation of two immiscible liquids • Aim: To separate a mixture of oil and water • Apparatus and materials: Separating funnel with tap, water, oil and 3 containers

Diagram:

Method • The apparatus was set up as shown in the diagram • The denser liquid at the bottom of the separating funnel was withdrawn through the tap and collected in a container • The container was then replaced with another and a small quantity of liquid was withdrawn (a mixture of the two right after the denser liquid was withdrawn

Method continued… • The container was then replaced again and the less dense liquid was allowed to run out and was collected. • Observations were noted

Observations • Two separate layers were formed in the separating funnel. • The oil was seen at the top layer and the water at the bottom layer

Discussion • The separation of two immiscible liquids is based on the principle that the two liquids do not mix and form two distinct layers • The less dense liquid was the oil, which formed the top layer • The denser liquid was the water which formed the bottom layer and was withdrawn first, allowing the separation of the two liquids

Conclusion • The mixture of oil and water was separated using a separating funnel • Oil and water are immiscible liquids because they do not dissolve one another

Application…. • The principle of immiscibility of liquids in some solvents is used in solvent extraction • Solvent extraction is used to separate a component from a mixture by using two solvents. • Two conditions have to be met: q. The component must be more soluble in one solvent than in the other q. The two solvents must be immiscible

For example…pg 75 • To compare the solubility of iodine in two solvents • Iodine is dissolved in water • The water is mixed with 1, 1, 1 trichloroethane • The iodine goes into this solvent and the water can be drained off in a separating funnel

Another example

Uses of solvent extraction • Good for removing organic molecules from water • For example caffeine from tea or coffee. • Caffeine is an organic compound which is more soluble in an organic solvent which is immiscible with water. (Dichloromethane)

Title: Paper Chromatography • Aim: To separate the components of screened methyl orange • Apparatus and materials: filter paper, beaker, capillary tube, test tube, screened methyl orange

Diagram:

Method: • To a strip of filter paper, a capillary tube was used to place a small drop of methyl orange, close to the base of the paper • A small volume of water was placed in a test tube or beaker • The strip of filter paper was suspended so that it barely touched the solvent

Method: • It was left to stand for a while • Observations were recorded

Observations • The liquid moved up the filter paper • Distinct colours could be seen • The colour that moved the furthest up the filter paper was…….

Observations

Discussion • Chromatography is a technique that uses a stationary phase and a mobile phase • The stationary phase is the filter paper in paper chromatography • The mobile phase is the solvent that moves up the paper • Chromatography can be used to separate minute quantities of substances.

Discussion • Separation of the different components occurs because each substance is soluble to different extents in the chosen solvent (the mobile phase) • The more soluble component travels the furthest up the filter paper and the least soluble remains closer to the base • Two colours were seen in screened methyl orange: two dyes a blue and a yellow

Conclusion • Screened methyl orange contains two components: a blue dye and a yellow dye • The more soluble component appeared blue in colour • The blue dye was more soluble in water

Applications of chromatography • Testing for trace contaminants in the environment • Monitoring water quality and air quality • Analyzing pure samples for trace contaminants (pharmaceutical industry) • Quality control in food industry