Qualitative Analysis

Question 1

Aluminium when NaOH is added?

Answer 1

White precipitate of aluminium hydroxide is formed which dissolves in excess to form a colourless solution

Question 2

Aluminium with ammonia

Answer 2

White precipitate is formed and insoluble in excess

Question 3

Zinc with a few drops of NaOH

Answer 3

White precipitate of zinc hydroxide is formed and dissolves in excess to form a colourless solution

Question 4

Lead with NaOH

Answer 4

White precipitate of lead hydroxide is formed which dissolves in excess to form a colourless solution

Question 5

Calcium with NaOH

Answer 5

White precipitate of calcium hydroxide is formed which is insoluble in excess

Question 6

Copper (II) with NaOH

Answer 6

Light blue precipitate of Copper (II) hydroxide formed and is insoluble in excess

Question 7

Iron (II) with NaOH

Answer 7

Green precipitate of Iron (II) hydroxide formed which is insoluble in excess. Turns red-brown when left to stand

Question 8

Ammonia with NaOH

Answer 8

No precipitate, ammonia gas is given off upon heating, turns red litmus paper blue. No observable change in excess.

Question 9

Zinc with ammonia

Answer 9

White precipitate of zinc hydroxide formed and dissolves in excess to form colourless solution

Question 10

Lead with ammonia

Answer 10

White precipitate of Lead hydroxide formed and is insoluble in excess

Question 11

Aluminium with ammonia

Answer 11

White precipitate of aluminium hydroxide formed and is insoluble in excess

Question 12

Calcium with ammonia

Answer 12

No precipitate formed and no observable change in excess

Question 13

Copper (II) with ammonia

Answer 13

Light blue precipitate of copper hydroxide formed and dissolves in excess to form a dark blue solution

Question 14

Iron (II) with ammonia

Answer 14

Green precipitate of Iron (II) hydroxide is formed and is insoluble in excess but turns red brown when left to stand

Question 15

Iron (III) with ammonia

Answer 15

Reddish-brown precipitate of iron (III) hydroxide is formed and is insoluble in excess

Question 16

Test for carbonate ion

Answer 16

Add dilute acid and bubble the gas into limewater. Carbonate + acid = Salt + water + CO2; limewater will turn chalky as gas will react with calcium carbonate to form a precipitate. Effervescence is given off and CO2 is produced

Question 17

Test for Nitrate Ion

Answer 17

Add NaOH and a piece of aluminium. Warm the mixture and use a damp litmus paper to test for the gas produced. Effervescence is observed and the red litmus paper turns blue if ammonia is produced

Question 18

Test for sulfate ion

Answer 18

Add dilute nitric acid then add aq barium nitrate. White precipitate of barium sulfate will be formed

Question 19

Test for Chloride ion

Answer 19

Add dilute nitric acid, then add aq silver nitrate. White precipitate of silver chloride will be formed

Question 20

Test for iodide ion

Answer 20

Add dilute nitric acid, then add aq silver nitrate. Yellow precipitate of silver iodide will be formed

Question 21

Why add dilute nitric acid

Answer 21

Dissolve impurities (usually carbonate) or to dissolve solid salt

Question 22

Why add aq barium/ silver nitrate

Answer 22

To form insoluble salt

Question 23

Test for Hydrogen

Answer 23

Place a burning/ lighted splint at the mouth of the test tube. Presence of hydrogen will make it extinguish with a pop sound

Question 24

Test for oxygen

Answer 24

Insert a glowing splint into the test tube. Presence of oxygen will make it rekindle

Question 25

Test for CO2

Answer 25

Bubble the gas through limewater. Presence of CO2 will cause a white precipitate to form. Precipitate will dissolve upon further bubbling

Question 26

Test for chlorine

Answer 26

It is a yellow-green gas with a pungent smell. But a damp blue litmus paper at the mouth of the test tube and it will turn red then bleached in the presence of chlorine

Question 27

Test for sulfur dioxide

Answer 27

A colourless pungent gas. Place a piece of filter paper soaked in acidified potassium manganate (VII) (KMNO4) at the mouth of the test tube. It will turn from purple to colourless in the presence of sulfur dioxide

Question 28

Test for ammonia gas

Answer 28

Colourless gas with a pungent smell. Place a piece of damp red litmus paper at the mouth of the test tube. It will turn blue in the presence of ammonia gas

Question 29

Test for water

Answer 29

1) Heat the salt. A colourless liquid in the form of condensation will appear at the mouth of the test tube in the presence of a hydrate salt

2) Test with anhydrous cobalt (II) chloride paper. It will turn from blue to pink in the presence of water

3) Test with anhydrous copper sulfate (s). It will turn from white to blue in the presence of water.