3.4 - Qualitative analysis

Question 1

Test for halogens

Answer 1

• add AgNO3 (aq)
• Cl- ions: white ppt
• Br- ions: cream ppt
• I- ions: yellow ppt

Question 2

Test for carbonate

Answer 2

• add dilute HNO3 (aq)
• produces CO2
• bubble gas (CO2) produced through limewater
• white ppt

Question 3

Test for sulfate

Answer 3

• add BaCl2 (aq) (BaNO3 (aq) if testing for halides after)
• white ppt

Question 4

Test for solubility of halogens

Answer 4

Cl: soluble in dilute
Br: soluble in conc
I: insoluble in both

Question 5

Sequence of tests

Answer 5

1. carbonate
2. sulfate (add excess)
3. halide (filter previous solution first)

Question 6

Test for ammonium ion

Answer 6

• heat with NaOH (aq)
• produces NH3 (g) which turns pH paper blue
  NH4+ + OH- -> NH3 + H2O

Question 7

How would you speed up the rate of these reactions for chemical tests?

Answer 7

heat test tubes in a water bath