Determining ions

Question 1

How to determine CO3 -2

Answer 1

• Dip in litmus paper - will turn paper Blue (as carbonate undergoes hydrolysis to produce hydrogen carbonate and hydroxide ions)
• Add strong acid (HCl and HNO3) observe bubbling and fizzing
• To validate CO2 production gas should turn limewater milky

Question 2

Determine Ba +2

Answer 2

Flame test - apple green,

Question 3

Determine Ca +2

Answer 3

Flame test - brick red

Question 4

Determine Pb +2

Answer 4

Add iodide ions - bright yellow precipitate

Question 5

Determine Ag +

Answer 5

Add halide ions, or SO4 -2

Question 6

Determine Cu +2

Answer 6

Flame test - blue-green
Complexations reaction add NaOH to form blue precipitate Cu(OH)2 –> then add ammonia solution and observe formation of a deep blue ter-tramindiaqua copper complex.

Question 7

Determine Fe +2

Answer 7

Oxidation: Add permanganate solution - will decolourise it (purple -> colourless)

Ass NaOH - forms green precipitate

Question 8

determine Fe +3

Answer 8

Complexation: add thiocyanate ions - forms blood red solution of iron(3)thiocyanate (SCN-)

Add NaOH - forms brown precipitate

Question 9

Determine Cl-

Answer 9

Add Ag+ and it will darken in the presence of UV

Question 10

Determine OH -

Answer 10

pH test - High pH

Question 11

Determine CH3COO-

Answer 11

Add alcohol and smell (ester)
Ass Ag+ - form white precipitate

Question 12

Determine PO4 -3

Answer 12

complexation: add conc nitric acid then ammonium molybdate solution - forms yellow precipitation

Yellow precipitate when adding Ag+