Tests For Ions

Question 1

How do we test for carbonates, then carbon dioxide?

Answer 1

Add dilute HCl, we should see fizzing due to carbon dioxide being formed.

Carbon dioxide can be tested for by bubbling it through lime water. If present like water should go cloudy.

Question 2

Sulfates.

Answer 2

Add dilute HCl, then Barium chloride.
If a sulfate present a white ppt should form of Barium sulfate.

Question 3

Halides (Chloride, Bromide, Iodide)

Then confirmation test

Answer 3

Add dilute silver nitrate solution

Chloride - white ppt
Bromide - cream ppt
Iodide - yellow ppt

Adding dilute Ammonia
Chloride - dissolves
Bromide - Doesn’t dissolve
Iodide - Doesn’t dissolve

Adding Concentration Ammonia:
Chloride - Dissolves
Bromide - Dissolves
Iodide - Doesn’t dissolve.

Question 4

Test for Ammonia

Answer 4

Test with damp red litmus.
If ammonia present it should turn blue.

Question 5

Ammonium?

Answer 5

Add NaOH and gently heat (Reduces ammonium into ammonia)
Test with damp red litmus. Should go blue.

Question 6

Hydroxides.

Answer 6

Dip red litmus in solution.
If hydroxides present it should turn blue.

Question 7

Nitrates

Answer 7

Warm solution with NaOH, and aluminum or Devadras alloy (reduces Nitrates to Ammonium).

Then test with damp red litmus, should turn blue.

Question 8

How do we avoid false positives

Answer 8

Test in the following order:
1. Test for carbonates
2. Test for sulfates
3. Test for halides

Or add dilute acid first.