Testing For Ions Flashcards
(19 cards)
How do you do flame tests?
- Use nichrome wire
- Dip into HCl & the flame to clean
- Dip into HCl amp gain & then into solid sample to test
- Hold in non-luminous Bunsen flame
What must the Bunsen flame be like for flame tests and why?
Non-luminous, which are orange
It would affect the flame colour
What material must the wire be for flame tests and why?
Nichrome
It’s very unreactive and has a high melting point
What colours are there for flame tests?
Lithium - red
Sodium - yellow
Potassium - lilac
Calcium - brick red
Copper - blue
How do you test for cations?
Flame test
How do you test for cations?
+ sodium hydroxide
What happens to copper (2) when you add NAOH?
Blue precipitate
Cu 2+ (aq) + 2OH - (aq) to Cu(OH)2 (s)
What happens to Fe(2+) when sodium hydroxide is added?
Green precipitate
Fe 2+ (aq) + 2OH- (aq) to Fe(OH)2 (s)
What happens to Fe 3+ when sodium hydroxide is added?
Brown precipitate
Fe 3+ (aq) + 3OH- (aq) to Fe(OH)3 (s)
What happens to ammonium when sodium hydroxide is added?
No precipitate
Solution need to be warmed, then gas released tested for ammonia
Damp red litmus paper will turn blue
Nh4 + (aq) + OH- (aq) to NH3 (g) + H20 (l)
How do you test for halides?
Dissolve in water, add dilute nitric acid then silver nitrate
What happens when chloride is dissolved in water, and nitric acid and silver nitrate is added?
White precipitate
Ag+ (aq) + Cl- (aq) to AgCl (s)
What happens when bromide is dissolved in water, and nitric acid and silver nitrate is added?
Cream precipitate
Ag+ (aq) + Br- (aq) to AgBr (s)
What happens when iodide is dissolved in water, and nitric acid and silver nitrate is added?
Yellow precipitate
Ag+ (aq) + I- (aq) to AgI (s)
How do you test for sulphates?
Add dilute hydrochloric acid then barium chloride
What is the result when testing for sulphates?
White precipitate
Ba 2+ (aq) + SO4 2- (aq) to BaSO4 (s)
How do you test for carbonates + what is the result?
Add acid (best to add nitric acid) look for bubbles & test using limewater which goes cloudy
CO3 2- (aq) + 2H+ (aq) to CO2 (g) + H20 (l)
What are the solubility rules for being soluble?
All nitrates
All sodium, potassium and ammonium
Common chlorides
Common sulphates
What are the solubility rules for being insoluble?
Common carbonates
Common hydroxides
Silver chloride
Lead chloride
Barium sulphate
Lead sulphate
Calcium sulphate
