qualitative analysis

Question 1

What order should you do anion tests in?

Answer 1

1- carbonates
2- sulphates
3- halide

Question 2

What compounds are insoluble?

Answer 2

barium carbonate BaCO3
silver sulphate Ag2SO4

Question 3

How can you identify carbonate ions?

Answer 3

• By adding an acid, which causes them to effervesce.

Question 4

What is the confirmatory test for carbonate ions?

Answer 4

Gas can be passed through limewater, as the CO2 will form a precipitate of CaCO3.

Question 5

What does the reaction look like for identifying carbonate ions!

Answer 5

CO32- + 2H+(aq) -> H20 (l) + CO2 (g)

Question 6

How can you identify sulphate ions?

Answer 6

• By adding barium nitrate solutions to form a precipitate of barium sulphate.

Question 7

Reaction showing identification of sulphate ions.

Answer 7

Ba2+(aq) + SO42- (aq) -> BaSO4 (s)

Question 8

How do identify halide ions and what are the results for chlorine, bromine and iodine?

Answer 8

• Identified from positive tests with acidified silver nitrate.
  cl -> white precipitate
  br -> cream precipitate
  I -> yellow precipitate

Question 9

What is the confirmatory test for halide ions?

Answer 9

cl -> dissolves in NH3
br -> dissolves in coc NH3
I -> insoluble in NH3

Question 10

How do you identify ammonium ions?

Answer 10

By warming them with NaOH(aq) to generate ammonia gas.

Question 11

What is the reaction to show the identification of ammonium ions?

Answer 11

NH4+ (aq) + OH-(aq) -> NH3 (g) + H20 (l)

Question 12

How can ammonia gas be identified?

Answer 12

• Gas can be identified by putting damp red litmus paper into the vapour, which will turn blue with NH3.