Chemical Reactions (DSE)

Question 1

Precipitation with NaOH/ NH3:
Mg2+

Answer 1

white ppt

Question 2

Precipitation with NaOH/ NH3:
Ag2+

Answer 2

white ppt

Question 3

Precipitation with NaOH/ NH3:
Cu2+

Answer 3

blue ppt

Question 4

Precipitation with NaOH/ NH3:
Fe3+

Answer 4

brown ppt

Question 5

Precipitation with NaOH/ NH3:
Fe2+

Answer 5

dirty green ppt

Question 6

Precipitation with NaOH/ NH3:
Pb2+

Answer 6

white ppt

Question 7

Precipitation with NaOH/ NH3:
Zn2+

Answer 7

white ppt

Question 8

Precipitation with NaOH/ NH3:
Al3+

Answer 8

white ppt

Question 9

What turns blue litmus paper red

Answer 9

acid (blood)

Question 10

What turns red litmus paper blue

Answer 10

alkali

Question 11

Fe displace Cu

Answer 11

Brown solid
Solution turns paler (lighter in colour)

Question 12

Zn displace Cu

Answer 12

Brown solid
Solution turns paler

Question 13

Mg displace Cu

Answer 13

Colorless bubbles
Brown solid

Question 14

Zn displaces Fe

Answer 14

Solution turns paler

Question 15

Mg displaces Fe

Answer 15

Colourless bubbles form

Question 16

Mg displace Zn

Answer 16

Colorless bubbles

Question 17

Heating/ Burning:
Potassium

Answer 17

Lilac

Question 18

Heating/ Burning:
Sodium

Answer 18

golden yellow flame

Question 19

Heating/ Burning:
Calcium

Answer 19

red flame, white solid

Question 20

Heating/ Burning:
Magnesium

Answer 20

burn with a very bright white light, and a white powder forms

Question 21

Heating/ Burning:
Aluminum

Answer 21

a white powder forms

Question 22

Heating/ Burning:
Zinc

Answer 22

Form a yellow powder when heated
White powder when cooled

Question 23

Heating/ Burning:
Iron

Answer 23

yellow sparks, black solid form

Question 24

Heating/ Burning:
Lead

Answer 24

orange powder when hot
yellow powder when cool

Question 25

Heating/ Burning:
Copper

Answer 25

black powder formed on the surface

Question 26

Heating/ Burning:
Mercury

Answer 26

red powder forms on the surface

Question 27

Give the warning label of hydrogen gas

Answer 27

Explosive, flammable

Question 28

Give the warning label of ethanol

Answer 28

Flammable

Question 29

Give the warning label of unburnt hydrocarbon

Answer 29

Carcinogenic

Question 30

Give the warning label of chlorine gas

Answer 30

Toxic

Question 31

Give the warning label of concentrated sulphuric acid

Answer 31

Corrosive, oxidizing

Question 32

Give the warning label of concentrated hydrochloric acid

Answer 32

corrosive

Question 33

How to test for chloride ion

Answer 33

Add acidified silver nitrate
white ppt form

Question 34

How to test for sulphate ion.

Answer 34

Add acidified barium chloride
white ppt form

Question 35

How to test for water (apart from dry cobalt (II) chloride paper)

Answer 35

anhydrous (dry) copper (II) sulphate turns from white to blue

Question 36

How to test for water ?

Answer 36

dry cobalt (II) chloride paper turns from blue to pink

Question 37

Heating alone: PbO

Answer 37

yellow solid

Question 38

Heating alone: CuO

Answer 38

black solid

Question 39

Heating alone: ZnO

Answer 39

white solid

Question 40

Heating alone: Fe2O3

Answer 40

black solid

Question 41

Heating alone: Ag2O

Answer 41

brown solid

Question 42

Heating CuO with carbon

Answer 42

Brown solid is formed

Question 43

Heating PbO with carbon

Answer 43

silver solid formed
Pbo changes from yellow to orange

Question 44

Heating Fe2O3 with carbon

Answer 44

silvery solid formed

Question 45

Heating ZnO with carbon

Answer 45

Silvery solid formed
ZnO changes from white to yellow