Qualitative and Quantitative Analysis and spectrometry

Qualitative Analysis

This refers to the process used to determine the elements present in a compound and what form they are in

Ways to test for Hydrogen

1. Using colorless anhydrous Copper Sulfate (CuSO₄)

2. Using Cobalt (II) Chloride (CoCl₂)

Test for Hydrogen using Copper Sulfate (CuSO₄)

The compound is heated with CuO (Copper (II) Oxide) and the gas produced is passed over anhydrous colorless CuSO4. A blue color change shows confirmation

Test for hydrogen using Cobalt (II) Chloride (CoCl₂)

The compound is heated with CuO and the gas is passed over Cobalt (II) Chloride. A color change from blue to pink shows confirmation.

Test for carbon

The compound is heated with CuO and the gas produced is passed over lime water. When the lime water turns milky it shows confirmation

Halogens

Elements that need one electron for their outermost shell to be complete

Examples of Halogens

Fluorine, Chlorine, Bromine, Iodine

Preparing Sodium Extract

Compound is heated with a sodium metal until it is red hot. the compound is dissolved in water and filtered.

Why is the compound heated with Sodium?

To make the compound soluble in water.

Sodium Fusion/ Lassaigne Test

This is a test used for the qualitative determination of halogens (except fluorine), Sulphur and Nitrogen

What compounds can interrupt the test for halogens?

Sulfate (SO₄^2- ) and Cyanide (C^-)

How eliminate Sulfate (SO₄^2- ) and Cyanide (CN^-)

Add Nitric acid (HNO₃ ) to the sodium extract and boil it

Confirmation of Chorine

After addition of AgNO₃ to the sodium extract a white precipitate that is soluble in excess NH₃ (Ammonia) is formed

Confirmation of iodine

After addition of AgNO₃ to the sodium extract a yellow precipitate that is insoluble in excess NH₃ (Ammonia) is formed

Confirmation of bromine

After addition of AgNO₃ to the sodium extract a pale yellow precipitate that is insoluble in excessNH₃ (Ammonia) is formed

Ways to Test for Sulphur

1. Using Lead acetate

2. using Sodium Nitroprusside

Test for Sulphur using Lead Acetate

10% of NaOH and this compound is added to the sodium extract. A black precipitate (PbS) is confirmation

Test for Sulphur using Sodium Nitroprusside

This compound is added to the sodium extract. A violet coloration shows confirmation

Test for Nitrogen

Iron (II) hydroxide (Fe(OH)₂ ) is added to the sodium extract and on further addition of iron(III) chloride (4FeCl₃ ). A prussian blue precipitate forming is confirmation

Test for Oxygen

No direct test for oxygen. Scientists add up other elements and any missing amount is oxygen.

Quantitative Analysis

The methods used to determine the amount of an element in an organic compound

Empirical Formula

This is the formula with the smallest whole number ratio of the elements in a compound

Molecular Formula

This formula shows the actual whole number ratio of elements in a compound

Formula for Molecular formula

Empirical formula*n

Spectrometry

The field of scientific study that measures and interprets electromagnetic spectra

Spectroscopic Methods

1. Infrared

2. Ultra Violet

3. Nuclear Magnetic Resonance

4. Mass Spectrometry

Infrared Spectroscopy

The spectrometry method used to determine the presence of functional groups

Ultra-violet

This spectrometry method is used to determine the presence or absence of conjugated pi-bonds

Nuclear Magnetic Resonance

This spectrometry is used to determine the structure of compounds at the atomic level

Mass Spectrometry

This is the spectrometry method used to measure the mass to charge ratio of ions. it is also used to determine the molecular mass and formula.