Tests for ions and Gasas Flashcards
How can metal ions be detected?
Metal ions can be detected using flame tests.
What is the purpose of dipping nichrome wire in hydrochloric acid?
To remove impurities.
What should you observe when holding the sample in a roaring Bunsen flame?
Observe the flame colour in the first few seconds.
What flame colour does Lithium (Li+) produce?
Red.
What flame colour does Sodium (Na+) produce?
Yellow.
What flame colour does Potassium (K+) produce?
Lilac.
What flame colour does Calcium (Ca2+) produce?
Orange-red.
What flame colour does Copper (Cu2+) produce?
Blue-green.
What happens when metal ions react with Sodium Hydroxide (NaOH)?
They form a coloured precipitate.
What is the colour of the precipitate for Copper (II) (Cu2+)?
Blue.
What is the chemical equation for Copper (II) precipitate formation?
Cu2+ (aq) + 2OH- (aq) 🡪 Cu(OH)2 (s).
What is the colour of the precipitate for Iron (II) (Fe2+)?
Green.
What is the chemical equation for Iron (II) precipitate formation?
Fe2+ (aq) + 2OH- (aq) 🡪 Fe(OH)2 (s).
What is the colour of the precipitate for Iron (III) (Fe3+)?
Brown.
What is the chemical equation for Iron (III) precipitate formation?
Fe3+ (aq) + 2OH- (aq) 🡪 Fe(OH)3 (s).
How can Ammonium ion (NH4+) be detected?
By adding sodium hydroxide solution, which releases ammonia.
What happens to damp red litmus paper when ammonia is produced?
It turns blue.
What test is used for Carbonates (CO3 2-)?
Add Hydrochloric acid and test for Carbon dioxide.
What indicates the presence of Carbon dioxide in the carbonate test?
Bubbling through limewater which turns milky.
What test is used for Sulphates (SO42-)?
Add Hydrochloric acid, then Barium Chloride to see a white precipitate.
What is the chemical equation for Sulphate precipitate formation?
Ba2+ (aq) + SO42- (aq) 🡪 BaSO4 (s).
What test is used for Halides (Cl-, Br-, I-)?
Add nitric acid then Silver Nitrate.
What is the result for Chloride (Cl-) in the halide test?
White precipitate.
What is the chemical equation for Chloride precipitate formation?
Cl- (aq) + Ag+ (aq) 🡪 AgCl (s).
What is the result for Bromide (Br-) in the halide test?
Cream precipitate.
What is the chemical equation for Bromide precipitate formation?
Br- (aq) + Ag+ (aq) 🡪 AgBr (s).
What is the result for Iodide (I-) in the halide test?
Yellow precipitate.
What is the chemical equation for Iodide precipitate formation?
I- (aq) + Ag+ (aq) 🡪 AgI (s).
What is the test for Oxygen gas?
It relights a glowing splint.
What is the test for Hydrogen gas?
A squeaky pop with a lighted splint.
What is the test for Carbon Dioxide?
Bubbled through limewater - turns cloudy.
What is the test for Chlorine gas?
Damp blue litmus paper turns red and then bleaches.
What is the test for Ammonia gas?
Turns damp red litmus paper blue.
What is the chemical reaction for the combustion of Hydrogen?
2H2 + O2 🡪 2H2O.
What indicates the presence of water?
White anhydrous copper sulphate turns blue.
What are the boiling and freezing points of pure water?
Pure water boils at exactly 100°C and freezes at 0°C.
What effect do impurities have on the boiling and freezing points of water?
Impurities will raise the boiling point and lower the freezing point.
