qualitative analysis

Question 1

blue solid

Answer 1

hydrated Cu2+ salts
(e.g. CuSO4.5H2O, Cu(NO3)2.3H2O

Question 2

green solid

Answer 2

Fe2+ compounds (e.g. FeSO4)
CuCO3

Question 3

red-brown solid

Answer 3

Fe3+ compounds (e.g. Fe(OH)3)

Question 4

yellow solid

Answer 4

AgI

Question 5

black solid

Answer 5

CuO
Iodine (I2)

iodine itself is solid

Question 6

grey solid

Answer 6

most metals
(e.g. Zn, Fe, Al metal)

Question 7

silver solid

Answer 7

Ag metal

Question 8

pink solid

Answer 8

Cu metal

Question 9

white solid

Answer 9

most other compounds
anhydrous CuSO4

Question 10

blue solution

Answer 10

Cu2+ (aq)
e.g. CuSO4 (aq), Cu(NO3)2 (aq)

Question 11

green solution

Answer 11

Fe2+ (aq)
e.g. FeSO4 (aq). FeCl2 (aq)

Question 12

yellow solution

Answer 12

Fe3+ (aq)
e.g. FeCl3 (aq)

Question 13

purple solution

Answer 13

KMnO4

potassium manganate

Question 14

orange solution

Answer 14

K2Cr2O7

potassium dichromate

Question 15

colourless solution

Answer 15

most other solutions

Question 16

tests for cations

Answer 16

adding aqueous sodium hydroxide to salt solutions
adding aqueous ammonia to salt solutions

Question 17

Na+ & K+

Answer 17

NaOH (aq):
- few drops: no precipate formed
- excess: no change

NH3 (aq):
- few drops: no precipitate
- excess: no change

Question 18

Al3+

Answer 18

NaOH (aq):
- few drops: white precipitate formed
- excess: precipitate soluble to form a colourless solution (sodium aluminate)

NH3 (aq):
- few drops: white precipitate
- excess: ppt insoluble

Question 19

Zn2+

Answer 19

NaOH (aq):
- few drops: white ppt formed
- excess: ppt soluble to form colourless solution (sodium zincate)

NH3 (aq):
- few drops: white ppt formed
- excess: ppt dissolves to form colourless solution

Question 20

Ca2+

Answer 20

NaOH (aq):
- few drops: white ppt formed
- excess: ppt insoluble

NH3 (aq):
- few drops: no ppt formed
- excess: no change

Question 21

NH4+

Answer 21

NaOH (aq):
- no ppt formed
- colourless pungent gas turns moist red litmus paper blue
- ammonia gas evolved

Question 22

Cu2+

Answer 22

NaOH (aq):
- few drops: pale blue ppt
- excess: ppt insoluble

NH3 (aq):
- few drops: blue ppt
- excess: ppt dissolves to form dark blue solution

Question 23

Fe2+

Answer 23

NaOH (aq):
- few drops: green ppt formed
- excess: ppt insoluble; ppt turned red-brown in contact with oxygen in air

NH3 (aq):
- few drops: green ppt formed
- excess: ppt insoluble; ppt turn red-brown in contact with oxygen in air

Question 24

Fe3+

Answer 24

NaOH (aq):
- few drops: red-brown ppt formed
- excess: ppt insoluble

NH3 (aq):
- few drops: red-brown ppt
- excess: ppt insoluble

Question 25

test for anions

Answer 25

checking for presence of:
ppt formed & solubility of ppt in acid
gas evolved

Question 26

carbonate CO3 2-

Answer 26

test: add dilute acid, pass gas given off into limewater
observations:
- effervescence observed
- colourless and odourless gas evolved
- gas forms white ppt with limewater
- CO2 (g) is evolved

Question 26

chloride Cl-

test for cl-

Answer 26

test: add aq silver nitrate, then add dilute nitric acid
observations: white ppt formed, ppt insoluble in dilute acid

Question 27

iodide (I-)

Answer 27

test: add aq silver nitrate, then add dilute nitric acid
observations: yellow ppt formed, ppt insoluble in dilute acid

Question 28

sulfate (SO4 2-)

Answer 28

test: add aq barium nitrate, then add dilute nitric acid
observations: white ppt formed, ppt insoluble in dilute acid

Question 29

nitrate (NO3-)

Answer 29

test: add aq sodium hydroxide. then add a little Devarda’s alloy (/piece of aluminum foil), warm the mixture. test gas given off with moist red litmus paper
observations: colourless pungent gas evolves that turns moist red litmus paper blue. NH3 (g) evolved.