Identification of Ions and gases

Question 1

List aqueous cations

Answer 1

Ammonium, copper (II), Iron (II), Iron (III) and zinc

Question 2

How are cations identified?

Answer 2

With Aqueous sodium hydroxide and aqueous ammonia

Question 3

Test for Ammonium cation and positive result

Answer 3

Add dilute sodium hydroxide, heat it.
Ammonia gas is released which has a pungent smell, damp red litmus paper turns blue

Question 4

Test for Copper (II) and positive result

Answer 4

Add dilute sodium hydroxide or ammonia solution. A blue precipitate forms

Question 5

Test for Iron (II) and positive result

Answer 5

Add dilute sodium hydroxide or ammonia solution. A pale green precipitate forms

Question 6

Test for Iron (III) and positive result

Answer 6

Add dilute sodium hydroxide or ammonia solution. A red brown precipitate forms

Question 7

Test for Zinc and positive result

Answer 7

Add dilute sodium hydroxide or ammonia solution. A white precipitate forms.

Question 8

What happens when a cation is given to identify but a precipitate doesn’t form when sodium hydroxide is added?

Answer 8

If there is no precipitate, gas may have formed. Use the litmus test on this gas to confirm that it is ammonia.

Question 9

List Anions

Answer 9

Carbonate, Chloride, Nitrate, Sulfate

Question 10

Test for Carbonates and positive result

Answer 10

Add dilute hydrochloric acid and limewater. Bubbles that give off gas will turn limewater milky

Question 11

Test for Chlorides and positive result

Answer 11

Add the same volume of nitric acid and chloride, add aqueous silver nitrate. A white precipitate will form

Question 12

Test for Nitrates and positive result

Answer 12

Add sodium hydroxide, then aluminium and warm gently. Ammonia gas is released which has a pungent smell, damp red litmus paper will turn blue

Question 13

Test for Sulfates and positive result

Answer 13

Add dilute hydrochloric acid and then a barium salt solution (could be chloride or nitrate). A white precipitate will form.

Question 14

what to do when given an anion to identify?

Answer 14

Divide in four test tubes and conduct the four tests above for each test tube.

Question 15

Colour of bromide ions positive

Answer 15

Pale yellow precipitate

Question 16

Test for ammonia gas

Answer 16

Damp red litmus paper turns blue

Question 17

Test for carbon dioxide

Answer 17

Pass it through limewater, it will turn milky white

Question 18

Test for chlorine gas

Answer 18

Damp blue litmus paper turns white

Question 19

Test for hydrogen gas

Answer 19

Expose it to a lighted splint, a loud pop sound is heard

Question 20

Test for oxygen gas

Answer 20

Expose it to a glowing splint, the splint will relight