Tests for Ions and Gases

Question 1

test for chlorine

Answer 1

Cl-
test: acidify with dilute nitric acid, then add aqueous silver nitrate
result: white precipitate (AgCl)

Question 2

test for bromine

Answer 2

Br-
test: acidify with dilute nitric acid, then add aqueous silver nitrate
result: cream precipitate (AgBr)

Question 3

test for iodine

Answer 3

I-
test: acidify with dilute nitric acid, then add aqueous silver nitrate
result: yellow precipitate (AgI)

Question 4

test for nitrate

Answer 4

NO3-
test: add aqueous sodium hydroxide, then aluminium foil, warm carefully
result: ammonia produced

Question 5

test for carbonate

Answer 5

CO3 2-
test: add dilute acid and test for CO2 gas
results: effervescence, CO2 produced

Question 6

test for sulfate

Answer 6

SO4 2-
test: acidify with dilute nitric acid, then add aqueous barium nitrate
result: white precipitate (BaSO4)

Question 7

test for sulfite

Answer 7

SO3 2-
test: add aqueous potassium manganate (VII) (KMnO4)
result: the acidified KMnO4 decolourises from purple to colourless

Question 8

test for ammonium

Answer 8

NH4 +
effect with aqueous sodium hydroxide: ammonia produced on warming

Question 9

test for calcium

Answer 9

Ca 2+
effect with aqueous sodium hydroxide: white precipitate, insoluble in excess
effect with aqueous ammonia:
no precipitate

Question 10

test for copper

Answer 10

Cu 2+
effect with aqueous sodium hydroxide: light blue precipitate, insoluble in excess
effect with aqueous ammonia: light blue precipitate, soluble in excess to form a dark blue solution

Question 11

test for iron (II)

Answer 11

Fe 2+
effect with aqueous sodium hydroxide: green precipitate, soluble in excess
effect with aqueous ammonia: green precipitate, insoluble in excess, turns brown at surface when standing

Question 12

test for zinc (II)

Answer 12

Zn 2+
effect with aqueous sodium hydroxide:
white precipitate, soluble in excess to form a colourless solution
effect with aqueous ammonia: white precipitate, soluble in excess to form a colourless solution

Question 13

test for aluminium

Answer 13

Al 3+
effect with aqueous sodium hydroxide: white precipitate, soluble in excess to form a colourless solution
effect with aqueous ammonia: white precipitate, insoluble in excess

Question 14

test for chromium (III)

Answer 14

Cr 3+
effect with aqueous sodium hydroxide:
green precipitate, soluble in excess
effect with aqueous ammonia:
green precipitate, insoluble in excess

Question 15

test for iron (III)

Answer 15

Fe 3+
effect with aqueous sodium hydroxide:
red-brown precipitate, insoluble in excess
effect with aqueous ammonia:
red-brown precipitate, insoluble in excess

Question 16

test for ammonia gas

Answer 16

NH3
result: turns damp red litmus paper blue

Question 17

test for carbon dioxide

Answer 17

CO2
result: turns limewater milky

Question 18

test for chlorine gas

Answer 18

Cl2
result: bleaches damp litmus paper

Question 19

test for hydrogen gas

Answer 19

H2
result: pops with a lighted splint

Question 20

test for oxygen gas

Answer 20

O2
result: relights glowing splint

Question 21

test for sulfur dioxide

Answer 21

SO2
result: turns acidified aqueous potassium manganate (VII) from purple to colourless

Question 22

flame test for lithium

Answer 22

Li+
red

Question 23

flame test for sodium

Answer 23

Na +
yellow

Question 24

flame test for potassium

Answer 24

K +
lilac

Question 25

flame test for calcium

Answer 25

Ca 2+
orange red

Question 26

flame test for barium

Answer 26

Ba 2+
light green

Question 27

flame test for copper (II)

Answer 27

Cu 2+
blue-green