Tests for Cations

Question 1

What do flame tests identify

Answer 1

metal ions

Question 2

What colour flame does Lithium , Li+ have

Answer 2

Red

Question 3

What colour flame does sodium, Na+ have

Answer 3

Yellow

Question 4

What colour flame does Potassium, K+, have

Answer 4

Lilac

Question 5

What colour flame does Calcium, Ca2+, have

Answer 5

Orange-red

Question 6

What colour flame does Copper, Cu2+, have

Answer 6

Blue-green

Question 7

What would you use to test a metal ions

Answer 7

Sodium hydroxide, NaOH
- add few drops of sodium hydroxide solution into your mystery compound in test tube
- if you get a coloured insoluble hydroxide you can tell which metal was present

Question 8

Colour precipitate and ionic equation of copper (II), Cu 2+

Answer 8

• Blue
• Cu2+ (aq) + 2OH- (aq) —> Cu(OH)2 (s)

Question 9

Colour precipitate and ionic equation of Iron (II), Fe 2+

Answer 9

-sludgy green
Fe2+ (aq) + 2OH- —> Fe(OH)2 (s)

Question 10

Colour precipitate and ionic equation of Iron (III), Fe3+

Answer 10

reddish brown
Fe3+(aq) + 3OH- (aq) —> Fe(OH)3 (s)

Question 11

What method can you use to test for ammonia gas

Answer 11

• damp piece of red litmus paper
• if ammonium ions is present, paper will turn blue

Question 12

Why does the litmus paper need to be damp

Answer 12

So the ammonia gas can dissolve and make the colour change

Question 13

What test is used to test whether a substance contain ammonium ions (NH4+)

Answer 13

• Add some sodium hydroxide
• if ammonia is given off, ammonium ions are present

Question 14

What does ammonium compound + NaOH give off

Answer 14

Ammonia