Qualitative Analysis

Question 1

What is qualitative analysis?

Answer 1

The use of chemical tests to determine information about the chemical you are studying.

Question 2

How to test for carbonate ions?

Answer 2

1. Add small amount of dilute HCL
2. Add unknown solution then immediate put a bung with delivery test tube.
3. Delivery tube should feed into test tube with lime water.
4. Positive result is effervescence and white precipitate.
   CO32- (aq) + 2H+ (aq) → CO2 (g) + H2O (l)
   CO2 (g) + Ca(OH)2 (aq) → CaCO3 (s) + H2O (l)

Question 3

Describe the test for Sulfates.

Answer 3

1. Add dilute HCL to acidify solution, then few drops of aqueous barium chloride.
   2.positive result is white precipitate.
   Can also be done with barium nitrate.
   Ba2+ (aq) + SO42- (aq) → BaSO4 (s)

Question 4

Describe the test for ammonium ions.

Answer 4

1.Add warm aqueous sodium hydroxide forming ammonia gas.
2.Identify via smell, bubbles or turning red litmus paper blue.
NH4+ (aq) + OH- (aq) → NH3 (g) + H2O (l)

Question 5

How do you test for Copper II ions?

Answer 5

Add dilute NaOH until in excess. Pale blue solution reacts to give blue ppt.
Insoluble in excess NaOH

Question 6

How do you tests for Iron II ions?

Answer 6

Add dilute NaOH (aq) until in excess. Pale green solution reacts to give green ppt. Insoluble in excess NaOH and excess NH3

Question 7

How do you test for iron III ions?

Answer 7

Add dilute Naoh (aq) until in excess. Yellow solution reacts to give orange-brown precipitate which darkens on standing. Insoluble in excess NaOH and NH3

Question 8

How do you test for Manganese II ions?

Answer 8

Add dilute NaOH (aq) until in excess. Pale pink solution reacts to form light brown precipitate. Insoluble in excess NaOH and NH3

Question 9

How do you tests for Chromium III ions?

Answer 9

Add dilute NaOH (aq) until in excess. Pale purple solution reacts to form grey-green ppt.
Soluble in excess NaOH, forming dark green solution. Soluble in excess NH3, forming purple solution.