Question

1.Use a permanent marker to label three test tubes "Carbonate Ion Test," "Sulfate Ion Test" and "Phosphate Ion Test.

2.Use the 10 mL graduated cylinder to measure and pour 2 mL of the unknown solution into each test tube.

3.Perform the Carbonate Ion Test by pipetting five drops of acetic acid into the test tube labeled "Carbonate Ion Test

4.Perform the Sulfate Ion Test by pipetting one drop of acetic acid (using the pipette from Step 5) and four drops of barium chloride (using a clean pipette) into the test tube labeled "Sulfate Ion Test.
5.Perform the Phosphate Ion Test by pipetting 2 mL of 0.1 M sodium phosphate tribasic into the test tube labeled "Phosphate Ion Test

My results: (Please correct me if I am wrong and explain) I may have had left over water in the tube, which affected my experiment.

Carbonate Ion Test: Bubbles & positive reaction

Sulfate Ion Test: Precipitate & positive reaction

Phosphate Ion Test: Precipitate & positive reaction (I believe, I messed up on this tube)

Question: Based on your lab results, what is the identity of the unknown solution?

A. calcium carbonate

B. phosphoric acid

C. nitric acid

D. sodium hydroxide

E. magnesium sulfate (my answer)

Answer 1

• Reaction of unknown solution with BaCl₂ gives white precipitate confirms sulphate ion whichis present only in option E, MgSO₄
• Reaction of acetic acid with MgSO₄ might have produced dut evolution gases as in the following reaction of MgSO₄ with acetic acid
• Reaction of MgSO₄ with acetic acid produces H2SO₄ which further may evolve slight ly SO2 and CO2 gases.( there is possibility because of bublles showing in the result)
• Reaction of sodium phosphate with MgSO4 gives a precipitate of magnesium phosphate.
• 3MgSO₄ + 2Na₃PO₄ --------------> 3Na₂SO₄ + Mg₃(PO4)₂(s)
• calcium carbonate cannot give white precipitate with BaCl2 but forms a hydrate
• options B,C,D are not at all possible.
• SO THE ANSWER GIVEN IS CORRECT. MgSO₄