Exp 6.1 B - To detect the presence of sulfate ions and sulfite ions in aqueous solution

Question 1

Apparatus required (4)

Answer 1

test-tube, dropper, spatula, wash bottle

Question 2

chemicals required (4)

Answer 2

any soluble sulfate salt solution (e.g. Na2SO4, K2SO4), any soluble sulfite salt solution (e.g. Na2SO3, K2SO3, BaCl2 [barium chloride] etc…), dilute HCl, deionised water

Question 3

List all 6 steps required in this experiment

Answer 3

1. Fill two test tubes to 1/4 full with a wash bottle of deionised water.
2. Add a small amount of sulfate salt to one test tube and a small amount of sulfite salt to the second test tube. Shake both to help dissolve. Label each test tube.
3. Add a few drops of barium chloride solution to the clear solution in each test tube.
4. Note observations. Both test tubes turn cloudy as a precipitate is formed.
5. To distinguish between the barium sulfate and barium sulfite, add about 1/4 test tube of dilute HCl to both test tubes and shake gently.
6. Note observations. The white precipitate remains in the test tube of sulfate ions as it is insoluble in dilute HCl. It dissolved in the test tube of sulfite ions as it is soluble in dilute HCl (Sulfate and remains both contain the letter A, sulfite and dissolve both contain the letter i)

Question 4

What is an easy way to remember the final observation after adding dilute HCl to the barium sulfate an sulfite

Answer 4

(Sulfate and remains both contain the letter A, sulfite and dissolve both contain the letter i)

Question 5

What are the results for this experiment after adding the dilute hydrochloric acid?

Answer 5

The white precipitate remains in the test tube of sulfate ions as it is insoluble in dilute HCl. It dissolved in the test tube of sulfite ions as it is soluble in dilute HCl

Question 6

Give the chemical formulas for the formation of the white precipitate

Answer 6

Ba2+ + SO4^2- –> BaSO4↓

Ba2+ + SO3^2- –> BaSO3↓

Question 7

Give the chemical equations for the adding of dilute HCl to the barium sulfate and sulfite solutions.

Answer 7

BaSo4 + HCl –> no reaction

SO3^2- + 2H+ –> SO2 + H2O

Question 8

Why does the cloudiness remain in the sulfate ions and disappear in the sulfite ions?

Answer 8

Barium sulfate is insoluble in dilute HCl.

Barium sulfite dissolves in dilute HCl.

Question 9

What are the conclusions of this experiment? (3)

Answer 9

Sulfate and sulfite ions are detected using barium chloride solution.
Sulfate and sulfite ions are distinguished from each other using dilute HC.
Barium sulfate is insoluble in dilute HCl but barium sulfite is soluble.