Qualitative Analysis (D)

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

Question 18

What occurs when aqueous sodium hydroxide is added to aqueous ammonia?

Answer 18

Ammonia gas is produced upon heating