tests for anions and cations

Question 1

test for halide ions using silver nitrate solution needs what

Answer 1

• dilute nitric acid (HNO₃)
• silver nitrate solution (AgNO₃ )

Question 2

why can’t you use hydrochloric acid when testing for halide ions

Answer 2

• you’d be adding chloride ions

Question 3

why when testing for halide ions does nitric acid have to be added first?

Answer 3

• to get rid of any carbonate ions - they produce a pale precipitate with silver nitrate and might confuse results

Question 4

what does a chloride ion make when silver nitrate is added

Answer 4

• it gives a white precipitate of silver chloride
• Ag⁺ + Cl^- → AgCl _(s)

Question 5

what does a bromide ion make when silver nitrate is added

Answer 5

• a bromide ion gives a cream precipitate of silver bromide
• Ag⁺ + Br^- → AgBr _(s)

Question 6

what does a iodide ion make when silver nitrate is added

Answer 6

• an iodide gives a yellow precipitate of silver iodide
• Ag⁺ + I^- → AgI _(s)

Question 7

how to test for carbonates using hydrochloric acid

Answer 7

• to test for carbonate ions

1. add some barium chloride solution
2. if there are carbonate ions a white precipitate of barium carbonate produced
3. then add dilute hydrochloric acid
4. if there are carbonate ions the mixture will fizz producing carbon dioxide
5. if gas is collected and pass through limewater the limewater should turn cloudy
6. once it has all reacted a colorless solution is formed containing Ba²⁺ ions

Question 8

what is the formula for carbonates

Answer 8

• BaCO₃+2H → Ba²⁺ + CO₂ +H₂O

Question 9

how to test for sulphate ions

Answer 9

1. add barium chloride solution
2. sulphate ions = white precipitate of barium sulphate
3. add dilute hydrochloric acid
4. barium sulphate wont react with hcl so white precipitate will not dissolve so
5. sulfate ions not carbonate ions

*

Question 10

what is the formula for testing sulfate ions

Answer 10

Ba⁺²+SO₄^2-→BaSO₄

Question 11

How can we test for metal ions?

Answer 11

1. Pit substance in flame
2. see what colors flame goes

Question 12

Describe the practical for finding metal ions

Answer 12

1. Clean nichrome wire look with hcl then rinse in deionised water
2. dip wire loop in metal compound
3. put Wire loop in blue flame of Bunsen burner
4. see what color it goes

Question 13

Explain the test for metal ions with sodium hydroxide

Answer 13

1. Add a few drops of sodium hydroxide solution to the unknown compound
2. if a hydroxide precipitate forms the color can be used to se what metal ion was in the compound

Question 14

What colour flame does Lithium, Li⁺ give

Answer 14

• Brick red

Question 15

What colour flame does Sodium, Na⁺ give

Answer 15

Yellow

Question 16

What colou flame does Potassium, K⁺ give

Answer 16

Lilac

Question 17

What coloured flame does Calcium, Ca²⁺ give

Answer 17

Orange-red

Question 18

What coloured flame does Barium, Ba²⁺give

Answer 18

Green

Question 19

What coloured flame does Copper, Cu²⁺ give

Answer 19