3.1.4 Qualitative analysis

Question 1

What is the method for testing carbonate ions?

Answer 1

1) add a strong acid to aqueous carbonate
2) collect any gas formed and pass it through limewater

If its fizzing or the limewater turns cloudy result is positive

Question 2

Ionic equation for carbonate ions?

Answer 2

Co3^2-(aq) + H^+(aq) = H2^+O(l) + Co2(g)

Question 3

Test for sulfate ions?

Answer 3

1) Add dilute hydrochloric acid and barium chloride to suspected sulphate
2)if white precipitate of baruim chloride is produced then the test is positive

Question 4

Ionic equation for sulfate ions?

Answer 4

Ba^2+ (aq) + so4^2-(aq) = Baso4 (s)

Question 5

Test for halide ions?

Answer 5

1) Add an aqueous solution of silver nitrate to the halide ion and look at the colour of precipitate.
2) Add dilute ammonia and look at solubility of the precipitate
3) add concentrated ammonia and look at solubility of precipitate

Question 6

Positive test observation for agcl,agbr,agi (halide ions)

Answer 6

agcl - White precipitate soluble in dilute ammonia
agbr - cream precipitate soluble in conc ammonia
agi - yellow precipitate insoluble in concentrated dilute and concentrated ammonia.

Question 7

in what order should qualitative tests be done for anions?

Answer 7

carbonate
sulfate
halide

Question 8

Test for the cation: ammonium

Answer 8

1) add sodium hydroxide solution to ammonium compound
2)warm gently
3) add litmus paper to any gas evolved

Question 9

positive test results for the ammonium ions?

Answer 9

ammonium gas has a distinctive smell
red litmus paper will turn blue

Question 10

ionic equation for ammonium ions?

Answer 10

NH4^+(aq) + OH^-(aq) = h20(l) + nh3(g)