Tests for Anions

Question 1

carbonate test

Answer 1

1. add dilute hydrochloric acid to your test sample
2. if carbonates are present then carbon dioxide will be released by effervescence
3. if this occurs, bubble the gas through limewater (to prevent false positives) and if carbonate ions were present the limewater will turn cloudy

Question 2

carbonate test word and symbol equation

Answer 2

carbonate + acid -> carbon dioxide + water

CO32- (s) + 2H+ (aq) -> CO2 (g) + H2O (l)

Question 3

sulfate test

Answer 3

1. add dilute hydrochloric acid and look for effervescence
2. if there is none, add barium chloride solution
3. if sulfate ions are present, they will form a white precipitate with the barium ions from the barium chloride
   NOTE: the hydrochloric acid is to get rid of any traces of carbonate or sulfite ions as both of these would also produce a precipitate)

Question 4

sulfate test word and symbol equation

Answer 4

barium ions + sulfate ions -> barium sulfate

Ba2+ (aq) + SO42- (aq) -> BaSO4 (s)

Question 5

halides test

Answer 5

1. dissolve the sample in water
2. add nitric acid (HNO3)
3. add silver nitrate (AgNO3) solution
4. if the halide ions are present, a precipitate forms with the silver ions from the silver nitrate
   NOTE: its important to add the HNO3 in step 2 because silver ions also form precipitates with other anions

Question 6

what colour precipitate does a chloride ion (Cl-) give?

Answer 6

white

Question 7

what colour precipitate does a bromide ion (Br-) give?

Answer 7

cream

Question 8

what colour precipitate does a iodide ion (I-) give?

Answer 8

yellow

Question 9

what is the ionic formula for the formation of silver chloride?

Answer 9

Ag+ (aq) + Cl- (aq)-> AgCl (s)

Question 10

what is the ionic formula for the formation of silver bromide?

Answer 10

Ag+ (aq) + Br- (aq) -> AgBr (s)

Question 11

what is the ionic formula for the formation of silver iodide?

Answer 11

Ag+ (aq) + I- (aq) -> AgI (s)