2g - chemical tests Flashcards
How do you test for hydrogen?
Method:
- collect gas in boiling tube
- Insert lit Splint inside the boiling tube
Result:
- If Hydrogen is present, the gas will burn with a ‘squeaky pop’
How do you test for oxygen?
Method:
- Collect gas into a boiling tube
- Insert glowing splint
Result:
- If Oxygen is present, splint will relight
How do you test for carbon dioxide?
Method:
- Bubble gas through limewater
- Observe colour change
Result:
- If Carbon Dioxide is present, limewater will turn milky and cloudy (form a white precipitate)
How do you test for ammonia?
Method
- Lower damp red litmus paper into the test solution
Results:
- If Ammonia is present, damp red litmus paper turns Blue
How do you test for chlorine?
Method:
- Lower damp blue litmus paper into test solution
Results:
- If Chlorine is present, damp litmus paper turns red then bleaches White
How do you carry out a flame test and what is it?
FLAME TEST: Method to identify Metal Cations by the colour of flame they produce
METHOD:
- Platinum or Nichrome wire is cleaned by dipping it into Hydrochloric acid
- End of wire is dipped into fresh Hydrochloric acid and then into solid sample
- End of the wire with solid sample attached is placed into a non-luminous bunsen flame
- Colour of flame is observed and recorded
What colour does the flame turn if lithium (Li⁺) is present?
bright red
What colour does the flame turn if sodium (Na⁺) is present?
golden yellow
What colour does the flame turn if potassium (K⁺) is present?
lilac
What colour does the flame turn if calcium (Ca²⁺) is present?
orange-red
What colour does the flame turn if copper (II) (Cu²⁺) is present?
Blue-Green
Who do you test for chloride ions? What is the equation for the reaction?
Method:
- Add a small volume of Dilute Nitric Acid to react and remove Carbonate ions from sample solution
- Add a few drops of Silver Nitrate Solution
- Colour of precipitate is observed and recorded
Results:
- If a white precipitate is formed then chloride ions are present
Equation:
Ag+ + Cl- → AgCl
Who do you test for bromide ions? What is the equation for the reaction?
Method:
- Add a small volume of Dilute Nitric Acid to react and remove Carbonate ions from sample solution
- Add a few drops of Silver Nitrate Solution
- Colour of precipitate is observed and recorded
Results:
- If bromide ions are present a cream precipitate will from
equation:
- Ag+ + Br- → AgNr
Who do you test for iodide ions? What is the equation for the reaction?
Method:
- Add a small volume of Dilute Nitric Acid to react and remove Carbonate ions from sample solution
- Add a few drops of Silver Nitrate Solution
- Colour of precipitate is observed and recorded
Results:
- If iodide ions are present then a yellow precipitate will from
Equation:
- Ag+ + I- → Agl
How do you test for sulphate ions?
Method:
- Add a small volume of Dilute Hydrochloric acid to react and remove Carbonate ions
- Add a few drops of Barium Chloride Solution
- Colour of precipitate is observed and recorded
result:
- If Sulfate ions are present, White precipitate will form (Barium Sulfate)
How do you test for carbonate ions?
Method:
- Add Dilute Hydrochloric acid
- Gas produced is bubbled into limewater
- Colour of precipitate is observed and recorded
Result:
- fizzing will occur
- If Carbonate ions are present, limewater will turn milky
How do you test for copper(II) ions?
Method:
- Add Aqueous Sodium Hydroxide
- Colour of precipitate is observed and recorded
Result:
- Blue Precipitate (solid)
Equation:
- Cu2+ + 2OH- → Cu(OH)2
How do you test for iron(II) ion?
Method:
- Add Aqueous Sodium Hydroxide
- Colour of precipitate is observed and recorded
Result:
- Green Precipitate will form (solid)
Equation:
- Fe2+ + 2OH- → Fe(OH)2
How do you test for iron(iii) ions?
Method:
- Add Aqueous Sodium Hydroxide
- Colour of precipitate is observed and recorded
Result:
- Brown precipitate will from (solid)
Equation:
- Fe3+ + 3OH- → Cu(OH)3
How do you test for ammonium ions?
Method:
- Add Aqueous Sodium Hydroxide to the solid or solution and heat using bunsen burner (warm it)
- Lower damp red litmus paper into gas produced
Result:
- If Ammonium ions are present, pungent-smelling gas is produced
- Gas produced turns damp red litmus paper Blue
How do you test for water?
Add anhydrous copper (II) sulfate (CuSO4) to a sample.
If water is present the anhydrous copper (II) sulfate will change from white to blue (into hydrated copper sulfate).
describe a physical test to show whether a sample of water is pure:
METHOD 1:
Boil liquid and measure boiling point
Result: Boiling point of Water is 100°C
METHOD 2:
Freeze liquid and measure freezing point (same as melting point)
result: Freezing point (melting point) of Water is 0°C
