Qualitative Analysis

Question 1

What is the colour and solubility of zinc precipitate in aqueous sodium hydroxide and ammonia?

Answer 1

NaOH: White (soluble in excess)
NH3: White (soluble in excess)

Question 2

What is the colour and solubility of aluminium precipitate in aqueous sodium hydroxide and ammonia?

Answer 2

NaOH: White (soluble in excess)
NH3: White (insoluble in excess)

Question 3

What is the colour and solubility of calcium precipitate in aqueous sodium hydroxide and ammonia?

Answer 3

NaOH: White (insoluble in excess)
NH3: No precipitate

Question 4

What is the colour and solubility of copper(II) precipitate in aqueous sodium hydroxide and ammonia?

Answer 4

NaOH: Light Blue (insoluble in excess)
NH3: Light Blue (soluble in excess which gives a dark-blue solution)

Question 5

What is the colour and solubility of iron(II) precipitate in aqueous sodium hydroxide and ammonia?

Answer 5

NaOH: Green (insoluble in excess)
NH3: Green (insoluble in excess)

Question 6

What is the colour and solubility of iron(III) precipitate in aqueous sodium hydroxide and ammonia?

Answer 6

NaOH: Red-Brown (insoluble in excess)
NH3: Red-Brown (insoluble in excess)

Question 7

What is the test and the observations for nitrate ion?

Answer 7

Test:
- Add aqueous sodium hydroxide (NaOH) and aluminium (Al) foil. Warm mixture gently

Results:
- ammonia gas given off which turns damp red litmus paper blue

Question 8

What is the test and the observations for carbonate ion?

Answer 8

Test:
- Add any dilute acid

Result:
- Carbon dioxide is produced
- Gas produced form white ppt (CaCO3) in limewater (Ca(OH)2)
- White precipitate dissolves more when more carbon dioxide passes into limewater

Question 9

What is the test and the observations for chloride ion?

Answer 9

Test:
- Add dilute nitric acid followed by silver nitrate

Result:
- White precipitate (AgCl) formed

Question 10

What is the test and the observations for iodide ion?

Answer 10

Test:
- Add dilute nitric acid followed by silver nitrate

Result:
- Yellow precipitate (AgI) formed

Question 11

What is the test and the observations for sulfate ion?

Answer 11

Test:
- add dilute hydrochloric acid followed by barium chloride
- OR add dilute nitric acid followed by barium nitrate

Result:
- White precipitate (BaSO4) formed

Question 12

What is the test and observations for ammonia gas?

Answer 12

Test:
- Place moist red litmus paper near the gas
- When ammonia dissolves in water, hydroxide ions are produced

Results:
- gas given off turns moist red litmus paper blue

Question 13

What is the test and observations for carbon dioxide gas?

Answer 13

Test:
- Bubble the gas into another test tube containing limewater

Result:
- Gas given off formed white precipitate when bubbled in limewater
- white precipitate dissolves with excess CO2

Question 14

What is the test and observations for chlorine gas?

Answer 14

Test:
- Place a piece of moist blue litmus paper near gas

Result:
- Gas given off turns moist blue litmus paper red and then bleached

Question 15

What is the test and observations for hydrogen gas?

Answer 15

Test:
- Place a lighted splint near the gas

Result:
- gas given off extinguished a lighted splint with a ‘pop’ sound

Question 16

What is the test and observations for oxygen gas?

Answer 16

Test:
- Place a glowing splint near the gas

Result:
- gas given off rekindled a glowing splint

Question 17

What is the test and observations for sulfur dioxide gas?

Answer 17

Test:
- Place a piece of filter paper soaked with acidified potassium manganate (VII) near the gas

Result:
- gas given off turned purple potassium manganate (VII), KMnO4, colourless