tests

• Describe the test for chlorine gas.


  In the test to identify chlorine, litmus paper is used. The litmus paper must be damp. Litmus paper turns white. When chlorine gas is present, litmus paper will be bleached and turn white.
• describe the test for hydrogen gas.


  the squeaky pop test. Holding a burning splint near to the top of the test tube. The positive result is a squeaky pop sound as the hydrogen reacts with oxygen in the air in a small explosion.
• Tests for gases

  • Hydrogen: a lit splint will burn with a squeaky pop.
  • Oxygen: a glowing splint will re-light.
  • Carbon dioxide: turns limewater milky.
  • Ammonia: turns damp red litmus paper blue. It also has a pungent odour.
  • Chlorine: turns damp blue litmus paper red before bleaching it white.
• describe the test for carbon dioxide


  You can test for Carbon Dioxide by bubbling the gas through limewater. If Carbon Dioxide is present the limewater will turn from colourless to a cloudy milky colour.
• describe the test for oxygen gas 


  take a glowing splint and place it in a sample of gas, if the flame re-ignites the gas is oxygen.
• describe the test for ammonia.


  Dip a glass rod in concentrated hydrochloric acid and put this in a sample of the gas and If ammonia is present, a white 'smoke' of ammonium chloride is observed.
• what is the alkene test?

  The test for alkenes is adding bromine water. If an alkene is present, the bromine water changes from orange to colourless.
•  Flame Test Method

  1. Clean a nichrome/platinum wire loop with dilute HCl, then heat in a blue flame.

  2. Dip the loop in the metal compound.

  3. Place in the roaring Bunsen burner flame.

  4. Observe and record the flame color.
• Lithium (Li⁺) Flame Color

  Crimson Red
• Sodium (Na⁺) Flame Color

  Yellow
• Potassium (K⁺) Flame Color

  Lilac purple
• Calcium (Ca²⁺) Flame Color

  Orange-Red
• Copper (Cu²⁺) Flame Color

  Green
• Aluminium (Al³⁺) with NaOH

  White precipitate (dissolves in excess NaOH)
• Sodium Hydroxide Test Method

  1. Add sodium hydroxide solution (NaOH) to the metal ion solution.

  2. Observe the precipitate color.

  3. If white, add excess NaOH to check if it dissolves.
• Calcium (Ca²⁺) with NaOH

  White precipitate (does NOT dissolve in excess NaOH)
• Magnesium (Mg²⁺) with NaOH

  White precipitate (does NOT dissolve in excess NaOH)
• copper(II) (Cu²⁺) with NaOH

  Blue precipitate
•  Iron(II) (Fe²⁺) with NaOH

  Green precipitate
• Iron(III) (Fe³⁺) with NaOH

  Brown precipitate
• How do you test for carbonate (CO₃²⁻) ions?

  • Add dilute acid

  • If carbonate is present → Fizzing (CO₂ gas produced)

  • Bubble gas through limewater → Turns cloudy
• How do you test for sulfate (SO₄²⁻) ions?

  • Add barium chloride and dilute hydrochloric acid

  • If sulfate is present → White precipitate forms
• How do you test for sulfate (SO₄²⁻) ions?

  • Add barium chloride and dilute hydrochloric acid

  • If sulfate is present → White precipitate forms
• How do you test for iodide (I⁻) ions?

  • Add dilute nitric acid

  • Add silver nitrate solution

  • Yellow precipitate forms
• How do you test for chloride (Cl⁻) ions?

  • Add dilute nitric acid

  • Add silver nitrate solution

  • White precipitate forms
•  How do you test for bromide (Br⁻) ions?

  • Add dilute nitric acid

  • Add silver nitrate solution

  • Cream precipitate forms
• What tests are used to identify positive cations and negative anions?

  Cations (+ Ions):

  • Flame Test

  • Sodium Hydroxide Test

  
  

  Anions (- Ions):

  • Carbonate Test

  • Sulfate Test

  • Halide Test (Silver Nitrate Test)
• Halide Test (Silver Nitrate Test) 

  → Add silver nitrate & dilute nitric acid:

  • Chloride (Cl⁻) → White precipitate

  • Bromide (Br⁻) → Cream precipitate

  • Iodide (I⁻) → Yellow precipitate
• Sulfate Test

   → Add barium chloride & dilute HCl → White precipitate forms.
• • Carbonate Test 

  → Add dilute acid → Fizzing (CO₂ gas produced, turns limewater cloudy).