This page contains the detailed and easy notes for Edexcel  IGCSE Chemistry Chemical Test for revision and understanding.

CHEMICAL TEST  

• Pure Substances
• Formulations
• Chromatography
• Test for Gases
• Test for Cation
• Test for Anions
• Instrumental Analysis

PURE SUBSTANCE

• Pure Substance is an element or a compound that is made up of only one substance.
• Pure substances have fixed melting and boiling point. Finding the melting and boiling points will provide the test for purity.
• Impurities makes the substance impure and alters the melting and boiling point.
• Impurities lowers the melting point but increases the boiling point.

FORMULATIONS

Mixtures made to make if useful for the mankind.

• Fuels
• Cleaning Agents
• Paints
• Medicines
• Alloys
• Fertilizers
• Foods

CHROMATOGRAPHY

• Components in the mixture are separated on the basis of solubilties of different components of the mixture in a suitable solvent.
• A capillary tube is used to spot the mixture on the chromatography paper.
• The paper is put inside a solvent and the solvent is allowed to run up the chromatography paper.
• The component of the mixture which is more soluble in the solvent will travel greater distance and will leave its mark near the top.’
• The component which is less soluble will have a mark near the bottom.

R_f  = S/L <  Distance travelled by solute

TEST FOR GASES

	Reaction	Test	Observation
Hydrogen	Metal higher in reactivity than hydrogen react with acid producing hydrogen	Bring a lighted splint to the mouth of the test tube containing hydrogen	The splint burns with the squeaky pop
Oxygen	Electrolysis of Water produced oxygen or decomposition of hydrogen peroxide	Bring a glowing splint to the mouth of the test tube containing oxygen.	The glowing splints relights.
Carbon Dioxide	Metal carbonate with dilute acids produce carbon dioxide	Pass the gas released to lime water	Limewater will turn milky
Chlorine	Electrolysis of brine	A damp blue litmus paper held at the mouth of the test tube	Bleached blue litmus paper

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 TEST FOR CATIONS

Nichrome wire dipped in concentrated hydrochloric acid

Heated

Dipped in acid again

Dipped in metal compound

Touched on the roaring blue bunsen flame

TEST FOR CATIONS

FLAME TEST              Add Aqueous Sodium Hydroxide

White Precipitate                                             Coloured Precipitate

Al³⁺           Mg²⁺          Ca²⁺                                 Cu²⁺         Fe²⁺      Fe³⁺

Soluble       No colour     Red

TEST FOR ANIONS

Carbonates CO32-	Halides Cl– Br– I–	Sulphates SO42-
Add dilute acid Effervescence of Carbon dioxide Pass to limewater  Limewater turns milky	Add dilute nitric acid  Add silver nitrate solution  Precipitate confirms thalide Yellow precipitate – Iodide Ions – I– Cream Precipitate – bromide ions -Br– White precipitate – chloride ions – Cl–	Add dilute hydrochloric acid Add barium chloride solution A white precipitate confirms sulphate

INSTRUMENTAL ANALYSIS

Flame emission Spectroscopy

• Each metal forms a characteristic line spectrum when placed inside a spectrometer.
• The line spectrum is compared with the database to detect the metal ion.
• The absorbance value gives the information about the concentration of metal ions.
• Can detect traces of metal ions in sample of air, steel or any other metal.

KEY TERMS

• Pure Substance – Pure Substance is an element or a compound that is made up of only one substance. Examples of pure substances include water, diamond, bronze, iron, silver and gold.
• Formulations – Mixtures made to make if useful for the mankind. It is a mixture of ingredients prepared in a certain way and used for a specific purpose.
• Chromatography – Components in the mixture are separated on the basis of solubilties of different components of the mixture in a suitable solvent.
• Mobile phase/moving phase – Solvent that moves through the column. Could be gas or liquid.
• Stationary phase/ nonmoving phase – substance that remains fixed inside the column.
• Flame emission Spectroscopy – Each metal forms a characteristic line spectrum when placed inside a spectrometer. The line spectrum is compared with the database to detect the metal ion.
• Chromatogram – A chromatogram is the visual output of the chromatograph
• Flame Test – A flame test is an analytical procedure used to detect the presence of some elements, mainly metal ions, depending on the characteristic of the emission spectrum of each element.
• Instrumental Analysis – Analytical chemistry studies and use the tools and methods used to separate, identify and quantify matter.

DISCLAIMER

Disclaimer: I have tried by level best to provide the answers and video explanations to the best of my knowledge. All the answers and notes are written by me and if there is any similarity in the content then it is purely coincidental. But this is not an alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.

References:

BBC Bitesize

Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.

C12-Chemical Analysis

• Identification of Common Gases 1 MS
• Identification of Common Gases 1 QP
• Identification of Common Gases 2 MS
• Identification of Common Gases 2 QP
• Identification of Common Gases 3 MS
• Identification of Common Gases 3 QP
• Identification of Ions by Chemical & Spectroscopic Means 1 MS
• Identification of Ions by Chemical & Spectroscopic Means 1 QP
• Identification of Ions by Chemical & Spectroscopic Means 2 MS
• Identification of Ions by Chemical & Spectroscopic Means 2 QP
• Identification of Ions by Chemical & Spectroscopic Means 3 MS
• Identification of Ions by Chemical & Spectroscopic Means 3 QP