Experimental Chemistry

Measurement:

The following table shows the appropriate apparatus needed for the measurement of time, temperature, mass and volume used in Experimental Chemistry.

Collection Of Gases:

Upward Delivery:

Upward delivery is used to collect gases that are less dense than air.

E.g. Hydrogen and Ammonia.

Downward Delivery:

Downward delivery is used to collect gases that are denser than air.

E.g. Chlorine and Hydrogen Chloride

 

Displacement Of Water:

Used for those gases which are insoluble in gases.

E.g. Hydrogen and Methane(CH₄)

 

 

Collecting Dry Samples of Gases:

We can dry a gas by passing a drying agent through them as these agents will absorb the moisture.

Drying Agents: Concentrated Sulphuric  Acid ( H₂SO₄ ), Quick Lime (Calcium Oxide (CaO))                   and Fused Calcium Chloride (CaCl₂).

Concentrated Sulphuric Acid is used to dry moist gases like Chlorine and HCL.However, it cant be used to dry Ammonia because it reacts with Ammonia.

 

Techniques For Seperation:

1. Filteration
2. Crystallization
3. Distillation
4. Fractional Distillation
5. Chromatography

 

Filteration:

It is used for separation of insoluble solid from a liquid.

Filtration is used to remove solid impurities from water/iquid.

Experiment:

• Place a filter paper into a filter funnel.
• Put the mixture of sand and water .
• The liquid will pass through as
• Sand as insoluble will remain on the filter paper as residue .

 

Crystallization:

It is an alternate method to recover a solute from its solution. The solution is evaporates to the crystallization point i.e. two points at which crystals of the solute will form on coolin. g, which can then be filtered out and dried.

 

Experiment:

1. Solution is heated, the water evaporates and the solution becomes concentrated.
2. The saturated solution is then allowed to cool, crystals will start to form.
3. The saturated solution is cooled to form, crystals that can be dried on a filter paper.
4. If evaporation needed we will evaporate but not 100% since if evaporated too much the crystals will convert themselves into powder.

Uses of Crystallization:

• Crystallization is used in obtaining pure sugar.
• Purification of antibiotics is used through crystallization.

 

Distillation:

Distillation is the method of obtaining a pure liquid (solute) from a solution of a solid (solute).

Distillation Flask:

In this the solution boils, liquid vaporizes and enters the condenser.

Condenser:

In the condenser liquid vapour cools and it turns into pure liquid.

Experiment:

1. Water is allowed to flow through the condenser.
2. Solution in the flask is heated.
3. Collect the desired liquid (solvent) as distillate in the beaker until the temperature starts to rise again.

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Important steps to be taken during distillation:

The thermometer shouldn’t be dipped into the solution; this ensures that the thermometer measures the boiling point of the substance that is being distilled.

The condenser consists of two tubes. The cold running water is allowed to enter the condenser from bottom and leave from the top.

The condenser slopes downwards, so that the pure solvent formed can run into the beaker.

If the distillate is volatile, the receiver can be put in a large container filled with ice.

Uses of Distillation:

• It is used to obtain pure water from sea water (desalination).

 

Fractional Distillation:

It is used to separate mixture of miscible liquids with different boiling points.

Fractionating Column:

Fractionating Column is a column containing glass beads/glass wool in it hence increasing the surface area, ensuring 100% separation and purification.

The water vapour condenses in the fractionating column and drops back into the flask, therefore insuring more purity.

 

The liquid with the lowest boiling will distill off first, as the fractionating column will condense the liquids with higher boiling point and therefore it will drop back into the flask.

The beaker can be changed after each liquid is distilled, to get other liquids.

The thermometer will be used to identify which liquid is getting distilled through its boiling point.

Uses of Fractional Distillation:

• It is used in industries to obtain Nitrogen, Argon and Oxygen from Air.
• It is used to separate crude oil into petrol, kerosene and other useful components.
• Fractional distillation is used to separate fermented liquor into ethanol and water.
• It is used to separate a mixture of miscible liquids.

 

Chromatography:

Chromatography is a process used to separate and identify two or more substances from a mixture. Also, it is used to find out the number of components in a liquid. Hence determining the purity of the substance.

Principles involved in chromatography:

• Each substance used, will have different solubility in the same solvent.
• If the substance is more soluble, it dissolve faster in the solvent. Hence greater the solubility of the substance greater the distance it will be carried away by the solvent, then that substance, which has less solubility.

 

A drop of the solution is placed on the origin line at the bottom of a chromatography paper.

Test For Aqueous Cations:

Test For Anions:

Test For Gases: