SC25c Test for Negative Ions

Question 1

example of halide ions? 4

Answer 1

Br-
F-
Cl-
I-

Question 2

what is the only soluble halide?

Answer 2

silver fluoride

Question 3

testing for halides steps?

Answer 3

~add a few drops of dilute nitric acid
~add a few drops of silver nitrate solution
~record the colour

Question 4

why do you add dilute nitric acid when testing for halide ions?

Answer 4

to acidify the solution and remove carbonate ion that might give a precipitate

Question 5

silver halide colours for chloride, bromide, iodide?

Answer 5

chloride, white
bromide, cream
iodide, yellow

Question 6

silver carbonate is an insoluble yellow solid. Suggest why dilute acid must first be added when testing solutions for halide ions using silver nitrate solution. 3 marks

Answer 6

~the acid reacts with any carbonate ions that may be present
~stopping a yellow precipitate of silver carbonate forming
~which would give a false positive result for iodide ions