SC25 Testing for Ions

Question 1

What solution is used in the test for positive ions

Answer 1

Sodium Hydroxide

Question 2

How does the test for metal ions work?

Answer 2

Dilute sodium hydroxide reacts with metal ions in solution forming a metal hydroxide.
Some of these are insoluble so form precipitates.

Question 3

What colour precipitate forms in the test for Aluminium (Al3+)

Answer 3

White

Question 4

What colour precipitate forms in the test for Calcium (Ca2+)

Answer 4

White

Question 5

What colour precipitate forms in the test for Copper (Cu2+)

Answer 5

Blue

Question 6

What colour precipitate forms in the test for Iron(II) (Fe2+)

Answer 6

Green

Question 7

What colour precipitate forms in the test for Iron(III) (Fe3+)

Answer 7

Brown

Question 8

How to test for amonium ions (NH4+)

Answer 8

Ammonium ions react with hydroxide ions forming ammonia + water
Warm the mixture
Ammonia gas is produced
Ammonia gas turns damp red litmus blue

Question 9

What colour precipitate do chloride ions form (Cl-)

Answer 9

White (Milk)

milchlorine

Question 10

What colour precipitate do bromide ions form (Br-)

Answer 10

Cream (Cream)

bream

Question 11

What colour precipitate do iodide ions form (I-)

Answer 11

Yellow (Butter)

I love butter

Question 12

What two solutions are added to test for hallide ions

Answer 12

Nitric acid to remove impurities
Silver Nitrate to form a precipitate

Question 13

Test for carbonate ions (CO3 2-)

Answer 13

Use a dilute acid (Usually HCl)
bubbles are formed if present
Limewater turns cloudy if the gas is carbon dioxide

Question 14

Test for sulphate ions (SO4 2-)

Answer 14

Barium ions react with sulphate ions to form a white barium sulphate precipitate

Question 15

Test for sulphate ions ionic equation

Answer 15

Ba 2+(aq) + SO4 2-(aq) → BaSO4(s)

Question 16

Test for hallide ions ionic equation

Answer 16

Cl- + Ag+ → AgCl

Cl- is replaced with the other hallide ions

Question 17

Test for ammonium ions ionic equation

Answer 17

NH4+(aq) + OH-(aq) → NH3(g) + H2O(l)