Chemical tests - Chemistry edexcel igcse

Test for hydrogen

Hold a lit split over the top of a the test tube and hear a squeaky pop sound

Test for oxygen

Blow out a lit split and then hover it over the tube, if oxygen is present it will relight

test for carbon dioxide

Bubble your solution through limewater, if CO2 is present it will turn a milky colour

Test for ammonia

Put damp red litmus paper in solution, if it ammonia is present it will turn blue

Test for chlorine

Put damp blue litmus paper in solution, if chlorine is present it will bleach the paper

Carrying out a flame test process (6 steps)

1. Dip a nichrome loop in HCl to clean

2. Put the nichrome loop in a roaring bunsen flame to clean

3. Dip the nichrome loop back in the HCl

4. Put the nichrome loop into a metal compound

5. Hover over a roaring bunsen flame

6. record the colour given off by the flame and repeat with other metals

Colour of Lithium flame (Li+)

red

Colour of Sodium flame (Na+)

yellow

Colour of potassium flame (K+)

lilac

Colour of Calcium (Ca2+)

red-orange

Colour of Copper (Cu2+)

blue-green

Describe a test for NH4+ (ammonium) using sodium hydroxide solution and identifying the gas evolved

Add sodium hydroxide solution and warm it. The smell of ammonia and damp red litmus paper will turn blue if present.

Using sodium hydroxide solution test for Cu2+ (copper)

Add a few drops of sodium hydroxide solution and a blue precipitate forms

Using sodium hydroxide solution test for Fe2+ (Iron (II))

Add a few drops of sodium hydroxide solution and a green precipitate forms

Using sodium hydroxide solution test for Fe3+ (Iron (III))

Add a few drops of sodium hydroxide solution and a brown precipitate forms

Testing for Cl-, Br- and I-

Add dilute nitric acid, then add silver nitate solution

Precipitates formed for Cl-, Br- and I-

White, cream, yellow

Testing for SO4²^- (sulfate)

Add dilute nitric acid then add barium chlrodie solution and a white precipitate will form

Testing for CO3²- (carbonate)

React with HCl and bubble the gas produced through limewater, if carbonate is present it will turn cloudy

Testing for the presence of water using anhydrous copper (II) sulfate

anhydrous copper (II) sulfate turns from white to blue on the addition of water

Show wheter a sample of water is pure (2 steps)

1. Place liquid in a boiling tube, heat gently

2. Using a thermometer you can check if the boiling point is exactly 100C (impurities tend to raise the boiling points)