Some common techniques for separation of a mixture
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Some Common Techniques for Separation of a Mixture. 1. Decanting. Separate a solid-liquid mixture based on difference in solubility or density. Decant = To gently pour off a liquid without disturbing the sediment (solid). 1. Decanting - continued.

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Some Common Techniques for Separation of a Mixture

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Some common techniques for separation of a mixture

Some Common Techniques for Separation of a Mixture


1 decanting

1. Decanting

Separate a solid-liquid mixture based on difference in solubility or density

Decant = To gently pour off a liquid without disturbing the sediment (solid)


1 decanting continued

1. Decanting - continued

When trying to decant and save an aqueous solution, it is often poured slowly down a stirring rod. The stirring rod acts as a pathway to direct the liquid. This method works because of the large intermolecular forces , IMFS between water molecules. The strength of the IMFs makes water molecules “sticky” – where one molecule goes the next is sure to follow.

Intermolecular forces are the attractions which occur between separate molecules


1 decanting continued1

1. Decanting - continued

Decanting would also work with two liquids of different density – but – it is easier to use a separatory funnel – a separatory funnel is sort of like “upside down” decanting


2 gravity filtration

2. Gravity Filtration

Separate a solid-liquid mixture by differences in solubility

Pour liquid – solid mixture to be separated through a filter paper

the insoluble substance (unable to be dissolved) will be caught on the filter, the soluble (able to be dissolved) substances will pass through as part of the filtrate

Let Gravity Do The Work!!!


3 vacuum filtration

3. Vacuum Filtration

Separate a solid-liquid mixture by differences in solubility

A special side-arm (vacuum) flask, called a Büchner Flask

are used together to filter a solid from solid-liquid mixture

and a special type of funnel called a Büchner Funnel

Let air pressure Do The Work!!!


3 vacuum filtration continued

3. Vacuum Filtration –Continued

The Büchner Flask is attached via a hose to a water nozzle and the water is turned on full blast!

The rushing water creates a vacuum in the Büchner Funnel (Bernoulli’s Principle). The atmospheric pressure then ‘pushes’ the filtrate through the filter paper and funnel. The insoluble substance is left on the filter paper.


4 chromatography

4. Chromatography

Separate a mixture based on preferential absorption of the constituents onto a paper strip.


Paper chromatography

Paper Chromatography

Solvent

Front

Filter paper

mixture

solvent

A piece of chromatography paper (the stationary phase) is ‘dotted’ with a sample of the mixture to be separated. The paper is placed into a solvent (the mobile phase) known to dissolve the sample.

The paper will wick up the solvent via capillaryaction (liquid rising against gravity due to IMFs). The sample dissolves in the advancing solvent front.

(c) The various constituents

(parts) of the mixture

move up at different rates

based on their mass, size,

charge, etc. Rf values are

then analyzed to

determine the compon-

entsof the mixture


Paper chromatography1

Paper Chromatography

Chromatogram = the paper strip on which all or some of the constituents of a mixture have been separated by being adsorbed at different locations

Origin= the point on the chromatography paper where the sample of the mixture is originally “dotted”

Rf values = the ratio of the distance a compound moved from the origin to the distance between the origin and the solvent front

Stationary Phase (chromatography paper)

Stationary Phase (chromatography paper)

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Beaker

Beaker

Mobile Phase (solution of NH3, butanol and water)

Mobile Phase (solution of NH3, butanol and water)


5 evaporation

5. Evaporation

Separate solid-liquid mixture by differences in boiling points

used to separate the constituents of a solution when the liquid portion, the solvent (thing that does the dissolving) has a much lower boiling point than that of the solid portion, the solute (thing that gets dissolved)

Could also be used to separate a suspension

This method is only good if there is no need to recover the solvent.

Stationary Phase (chromatography paper)

Stationary Phase (chromatography paper)

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Beaker

Beaker

Mobile Phase (solution of NH3, butanol and water)

Mobile Phase (solution of NH3, butanol and water)


6 distillation

6. Distillation

Separate liquid-liquid or liquid-solid mixture by differences in boiling points

Use when ALL the components of a mixture must be recovered

- best for separation of two different liquids

Stationary Phase (chromatography paper)

Stationary Phase (chromatography paper)

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Beaker

Beaker

Mobile Phase (solution of NH3, butanol and water)

Mobile Phase (solution of NH3, butanol and water)


Distillation continued

Distillation - continued

The distillate or condensate is the purified component of the mixture

the distilling flask iswhere the original mixture is heated

the condenser

Stationary Phase (chromatography paper)

Stationary Phase (chromatography paper)

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Beaker

Beaker

Mobile Phase (solution of NH3, butanol and water)

Mobile Phase (solution of NH3, butanol and water)


7 magnetism

7. Magnetism

Separate the components of a mixture based on differences in magnetism

In a simple example, a mixture of iron filings and sulfur powder are separated from one another using a magnet.

Stationary Phase (chromatography paper)

Stationary Phase (chromatography paper)

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Beaker

Beaker

Mobile Phase (solution of NH3, butanol and water)

Mobile Phase (solution of NH3, butanol and water)


Magnetism

Magnetism

In a more complicated example, a magnet is used to bend the path of heavy and light (mass) charged particles (isotopes, molecules, molecular fragments) to separate the components of a mixture on an atomic or molecular level. The

equipment used to accomplish this is called a mass spectrometer.

Stationary Phase (chromatography paper)

Stationary Phase (chromatography paper)

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Starting Line

Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid!

Beaker

Beaker

Mobile Phase (solution of NH3, butanol and water)

Mobile Phase (solution of NH3, butanol and water)


Vocab

Vocab

  • Büchner flask

  • Büchner funnel

  • Capillary action

  • Chromatogram

  • Chromatography

  • Chromatography, paper

  • Condensate

  • Condenser

  • Component(s)

  • Constituent(s)

  • Decant(ing)

  • Distillate

  • Distillation

  • Distilling flask

  • Filtrate

  • Filtration

  • Filtration, gravity

  • Filtration, vacuum

  • Insoluble

  • Intermolecular forces (IMFs)

  • Mass spectrometer

  • Mobile phase

  • Sediment

  • Soluble

  • Solute

  • Solution

  • Solvent

  • Solvent front

  • Stationary phase

  • “Wick up”


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