c4 - chemical changes

Question 1

what are unreactive metals known as?

Answer 1

unreactive metals are found in the Earth as the metal itself.
They are known as ‘pure metals’

Question 2

To extract the metal from the oxide, we need to
use a chemical reaction.
how can we do this?

Answer 2

There are 2 ways:

1. Displacement Reactions
2. Reduction using carbon

Question 3

what is meant by a displacement reaction?

Answer 3

A more reactive element will push out (displace) a less reactive element from its compound.

eg
magnesium + iron oxide –> magnesium oxide + iron
Any element higher than iron would be able to displace the oxide

but these elements are really expensive so in practice, we use carbon that is cheaper.

Question 4

what is extracting metals using carbon?

Answer 4

Carbon is a non-metal that likes to react with oxygen
more than the metals below it in the reactivity series

Question 5

what is oxidation in terms of oxygen

Answer 5

gain of oxygen

Question 6

what is reduction in terms of oxygen

Answer 6

loss of electrons

Question 7

what is oxidation in terms of electrons
(OILRIG)

Answer 7

oxidation is loss of electrons

Question 8

what is reduction in terms of electrons
(OILRIG)

Answer 8

reduction is gain of electrons

Question 9

examples of 3 strong acids

Answer 9

-hydrochloric acid (HCl)
-sulfuric acid (H^2SO^4)
-nitric acid (HNO^3)

Question 10

what are the two ways we measure pH

Answer 10

-pH probe
-universal indictor

Question 11

what ions do acids form

Answer 11

H+ ions (hydrogen ions)

Question 12

what ions do acids form

Answer 12

OH- ions (hydroxide ions)

Question 13

what is the difference between a strong and weak acid

Answer 13

strong acids fully ionise
weak acids partially ionise

Question 14

metal oxide + acid –> __________

Answer 14

salt + water

Question 15

metal hydroxide + acid –> _______________

Answer 15

salt + water

Question 16

metal carbonate + acid –> _______________

Answer 16

salt + water + carbon dioxide

Question 17

what do these acids form

1) sulfuric acid
2) hydrochloric acid
3) nitric acid

Answer 17

1) sulphate
2) chloride
3) nitrate

Question 18

what do we use to extract from the reactivity series

potassium
sodium
calcium
magnesium
aluminium
CARBON
zinc
iron
tin
lead
HYDROGEN
copper
silver
gold
platinum

Answer 18

potassium to aluminum:
most reactive metals extracted using electrolysis

carbon to lead :
extracted using reduction with carbon

hydrogen to platinum :
inert = unreactive

Question 19

making salts practical for
copper sulphate crystals

Answer 19

1) measure 40 cm^3 of sulfuric acid using a measuring cylinder and pour it into a beaker
2) set up the bunsen burner using a heatproof mat, a tripod and a gauze
3) heat the sulfuric acid until warm
4) turn the gas off and using a spatula, add the copper oxide and mix it with a stirrer
5) repeat adding copper oxide until in excess - black powder at the bottom of the beaker so all sulfuric acid has reacted
6) with funnel paper fold twice and place into a funnel with a conical flask under
7) pour the mixture into the funnel paper and with the remaining solution add into a crystallisation dish (evaporating basin)
8) leave overnight for crystallisation to occur for copper sulfate crystals to form.

Question 20

what is electrolysis?

Answer 20

using electricity to split something up

Question 21

can solid ionic compounds conduct electricity?

Answer 21

Solid ionic compounds CANNOT conduct electricity

Why?

The ions are locked in place and are NOT FREE TO MOVE

Question 22

what does the ionic compound need to be in order to carry out electrolysis?

Answer 22

1. Dissolved in water
2. Molten (melted)

Why?

So the forces of attraction are broken and the IONS ARE FREE TO MOVE so the
ions can now conduct electricity

Question 23

what is the negative electrode known as?

Answer 23

cathode (covered with electrons)

Question 24

what is the positive electrode known as?

Answer 24

anode (lack of electrons)

Question 25

what does molten lead bromide break up into

Answer 25

Pb 2+
2Br-

Question 26

half equation of Pb2+ and 2Br-

Answer 26

Pb(2+) + 2e(-) –> Pb (reduction)

2Br(-) - 2e(-) –> Br 2 (oxidation)

Question 27

what is aluminium known as ?

Answer 27

Bauxite

Question 28

what do we need to add to aluminium to lower the melting point?

Answer 28

cryolite

Question 29

half equation of Al(3+) and O(2-)

(aluminium oxide)

Answer 29

Al(3+) + 3e(-) –> Al

2O(2-) - 4e(-) –> O2

Question 30

what are the rules of the CATHODE?

Answer 30

-if the metal is more reactive than hydrogen then HYDROGREN is produced
-If the metal is less reactive then a metal is produced

Question 31

what are the rules of the ANODE?

Answer 31

-If halide (group 7) is present then the halogen is produced
-If halide is not present then water and oxygen is made

Question 32

half equation of NaCl ?

NaCl is broken into Na+ and Cl-

H20 is also produced which makes H+ and OH- ions.

Answer 32

Anode: Cl- is produced

half equation: 2Cl(-) - 2e(-) –> Cl2 (oxidation)

Cathode: H+ is produced

half equation: 2H(+) + 2e(-) –> H2
(reduction)

Question 33

why is the anode replaced regularly?

Answer 33

The oxygen molecules produced at the anode react with
graphite (carbon), forming carbon dioxide gas

Question 34

why is electrolysis expensive?

Answer 34

1. Melting the compounds such as aluminium coxide requires
   a great deal of energy
2. A lot of energy is required to produce electric current

Question 35

What is meant by an aqueous solution?

Answer 35

Aqueous solutions are dissolved in water

Water splits to form hydrogen ions and hydroxide ions

Question 36

what does copper sulfate solution produce
(CuSO4)

Answer 36

Because we have dissolved it in water… we
have:
[ Cu(2+) SO4 (2-) ]
H+ ions and OH- ions

Question 37

from copper sulfate what is produced at the anode and cathode?

Answer 37

anode: oxygen and water

cathode: copper

Question 38

half equation of CuSO4

Answer 38

Cu (2+) + 2e(-) –> Cu (reduction_

4OH(-) –> O2 + 2H(2)O + 4e(-)
4OH(-) - 4e(-) –> O2 +2H(2)O