Qualitative analysis: Tests for ions

Question 1

What colour does each metal cation turn in flame test?

Sodium, potassium, calcium, lithium, copper

Answer 1

Sodium, Na+ - Orange-yellow
Potassium, K+ - Lilac
Calcium, Ca2+ - Red-orange
Lithium, Li+ - Red
Copper,Cu2+ - Blue-green

Question 2

Colour of precipitation and further results (if necessary) for confirmatory/precipitation test? Aluminium, calcium, copper(II), iron(II), iron(III), ammonium

Answer 2

Aluminium, Al3+ - White, dissolves
Calcium, Ca2+ - White, doesn't dissolve
Copper(II), Cu2+ - Blue
Iron(II), Fe2+ - Green
Iron(III), Fe 3+ - Blue
Ammonium, NH4+ - Gives off ammonia gas

Question 3

Method for flame test?

Answer 3

Dip nichrome wire in concentrated HCl acid then heat either on blue flame.
Dip again in HCl then pick up solid and hold wire in blue flame

Question 4

Method for confirmatory test?

Answer 4

Dissolve half spatula of solid in 1cm depth water in test tube.
Use pipette to add few drops of NaOH solution and note colour of precipitate that forms.
Add more NaOH solution to see if precipitate will dissolve

Question 5

Method for ammonium ions?

Answer 5

Dissolve half spatula of solid in 1 cm of water in test tube.
Use pipette to add few drops of NaOH solution and warm gently by placing tube in beaker of hot water.
If ammonium ions are present, ammonia gas given off. Red litmus paper will turn blue if present.

Question 6

Method for sulfate test?

Answer 6

Dissolve half spatula of solid in 1cm depth of water in test tube.
Add equal volume of HCl acid and 5 drops barium chloride solution and note

Question 7

Method for halide (chloride, bromide, iodide) test?

Answer 7

Dissolve half spatula of solid in 1cm depth water in test tube.
Add equal volume of nitric acid and 5 drops silver nitrate solution and note

Question 8

Method for carbonate test?

Answer 8

Add half spatula of solid to boiling tube.
Add 3cm depth HCl acid and look for fizzing
If fizzes, fix bung and delivery tube to boiling tube and bubble gas through test tube of limewater. Note changes to limewater

Question 9

3 test names for positive metal ions?

Answer 9

Flame, confirmatory and ammonium

Question 10

3 test names for negative non-metal ions?

Answer 10

Sulfate, halid (chloride, bromide, iodide), carbonate

Question 11

Colour of precipitate for halide ions? Chloride, bromide, iodide

Answer 11

Chloride, Cl- - Silver white
Bromide, Br- - Off-white
Iodide, I- - Pale yellow