5.2.5 - anion tests

Question 1

what are anions

Answer 1

negative ions

Question 2

how do you test for halide ions (Cl-, Br- and I-)

Answer 2

silver nitrate test:

1) dissolve sample in water
2) add nitric acid (HNO3)
3) add silver nitrate (AgNO3) solution

if halide ions are present, a precipitate forms with the Ag+ ions from the AgNO3

Question 3

what colour does Cl- turn in the silver nitrate test

Answer 3

white

Question 4

what colour does Br- turn in the silver nitrate test

Answer 4

cream

Question 5

what colour does I- turn in the silver nitrate test

Answer 5

yellow

Question 6

testing for carbonates:

Answer 6

1) add HCl, look for effervescence
2) if there is effervescence, bubble the gas through limewater

if CO3^2- ions were present in the sample, the gas turns the limewater cloudy

Question 7

testing for sulphates:

Answer 7

1) add HCl, look for effervescence
2) if there is no effervescence, add barium chloride (BaCl2) solution

if SO4^2- ions are present, they will form a white precipitate