qualitative analysis 🌗

Question 1

Ca2+ observation in NaOH and NH3

Answer 1

NaOH: white ppt, insoluble in excess
NH3: no ppt

Question 2

NH4+ observation in NaOH and NH3

Answer 2

NaOH: no ppt. on heating, ammonia gas is evolved
NH3: NIL

Question 3

Zn2+ observation in NaOH and NH3

Answer 3

NaOH: white ppt, soluble in excess
NH3: white ppt, soluble in excess

Question 4

Al3+ and Pb2+ observation in NaOH and NH3

Answer 4

NaOH: white ppt, soluble in excess
NH3: white ppt, insoluble in excess

Question 5

Cu2+ observation in NaOH and NH3

Answer 5

NaOH: light blue ppt, insoluble in excess
NH3: light blue ppt, soluble in excess to form a deep blue solution

Question 6

Fe2+ observation in NaOH and NH3

Answer 6

green ppt, insoluble in excess

Question 7

Fe3+ observation in NaOH and NH3

Answer 7

reddish-brown ppt, insoluble in excess

Question 8

test for SO4 2- ions

Answer 8

add dilute nitric acid followed by aqueous barium nitrate. white ppt formed

Question 9

test for Cl- ions

Answer 9

add dilute nitric acid followed by aqueous silver nitrate. white ppt formed

Question 10

test for I- ions

Answer 10

add dilute nitric acid followed by aqueous silver nitrate. yellow ppt formed

Question 11

test for CO3 2-

Answer 11

add dilute acids, carbon dioxide evolved

Question 12

test for NO3- ions

Answer 12

add dilute NaOH and aluminium foil and warm, ammonia gas produced

Question 13

test for hydrogen gas

Answer 13

gas produced extinguishes a lighted splint with a ‘pop’ sound

Question 14

test for carbon dioxide gas

Answer 14

gas produced forms white ppt in limewater

Question 15

test for ammonia gas

Answer 15

gas produced turns moist red litmus paper blue

Question 16

test for oxygen gas

Answer 16

gas produced relights a glowing splint

Question 17

ZnO colour change

Answer 17

yellow when hot, white when cooled