PAG 04: Qualitative analysis of ions

Question 1

Describe chemical test for halide ions

Answer 1

Add dilute nitric acid to react with carbonate ions so no Ag2CO3 forms (white solid)
Add silver nitrate. Precipitate forms:
- White: AgCl (soluble in dilute ammonia)
- Cream: AgBr (soluble in concentrated ammonia)
- Yellow: AgI (insoluble in ammonia)

Question 2

How can SO4^2- ions be identified?

Answer 2

Add aqueous barium nitrate. A white precipitate (BaSO4) will form if sulfate ions are present. This precipitate is insoluble in excess dilute strong acids.

Question 3

Describe chemical test used to detect CO3^2- and HCO3^- ions

Answer 3

• Add aqueous acid
• If either ion is present, bubbles of CO2 will be released
• Test the gas by bubbling it through limewater via a delivery tube. If it is CO2, the limewater will turn cloudy

Question 4

What are solubilities of first 3 group 2 metals (Mg, Sr, Ba) in sulfate solution?

Answer 4

Mg- soluble
Sr- insoluble
Ba- insoluble

Question 5

What are solubilities of first 3 group 2 metals (Mg, Sr, Ba) in chromate solution?

Answer 5

Mg- soluble
Sr- soluble
Ba- insoluble