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Question 1

Cell

Answer 1

A redox system which contains chemicals that react together to create electrical energy

Question 2

Structure

Answer 2

Two metals in contact with an electrolyte

Question 3

Size of PD depends on

Answer 3

Type of electrode
Concentration of electrolyte

Question 4

Battery

Answer 4

2 or more cells connected in series

Question 5

Non rechargeable batteries

Answer 5

Reaction at electrodes is irreversible
When all reactants run out, no voltage produced

Question 6

Rechargeable batteries

Answer 6

Reaction at electrodes is reversible
Connect battery to pins and reverse current through it

Question 7

Fuel cell

Answer 7

A cell which generates an electrical current as long as fuel and O2 are supplied

Question 8

Negative electrode

Answer 8

H2 converted to H+ oxidation
H2 (g) -> 2H+ + 2e-

H+ travels through electrolyte
e- travels into electrical circuit generating a current

Question 9

Positive electrode

Answer 9

H+ reacts w oxygen to form water reduction

4H+ (aq) + 4e- + O2 -> 2H2O

Question 10

Overall reaction fuel cell

Answer 10

2 H2 (g) + O2 (g) -> 2 H2O (g)

Question 11

Advantages of fuel cells

Answer 11

More accessible materials
Lower emissions
No toxic fumes
Fuel added makes it last longer

Question 12

Disadvantages of fuel cells

Answer 12

Less accessible fuels
Less available infrastructure
H2 is explosive

Question 13

Corrosion

Answer 13

The gradual destruction of materials by reaction with substances in the environment

Question 14

Rust

Answer 14

The corrosion of iron
Forms hydrated iron oxides and hydroxide

Question 15

Hydroxide ions half equation

Answer 15

4e- + O2 + 2H2O -> 4OH-

Question 16

Iron ions half equation

Answer 16

Fe -> Fe 2+ + 2 e-

Question 17

Iron further oxidised

Answer 17

Fe 2+ + O2 -> Fe 3+ + 2O2-

Question 18

Iron hydroxides break down into oxides releasing water

Answer 18

Fe (OH) 2 -> FeO + H2O

Question 19

Barrier method of preventing corrosion

Answer 19

Coating with paint or plastic
Oiling or greasing
Electroplating with less reactive metal

O2 and H2O cannot get to surface

Question 20

Sacrificial protection

Answer 20

Blocks of more reactive metal corrode in place of less reactive metal

Galvanising adds a coat of zinc to stop O2 and H2O reaching surface

If scratched, Zn corrodes and not Fe

Question 21

Low carbon steel

Answer 21

Easily shaped
Car bodies

0.1 to 0.3

Question 22

High carbon steel

Answer 22

Strong but brittle
Construction
0.25 to 0.5

Question 23

Stainless

Answer 23

Resists corrosion
Cutlery

Cu/Ni

Question 24

Higher carbon content means

Answer 24

Harder for layers to slide, so higher CC = less malleable = less easy to slide = more brittle

Question 25

Why is Chromium used in steel (iron alloys)

Answer 25

More reactive, adding sacrificial protection, reducing corrosion

Question 26

Aluminum - why unpainted?

Answer 26

Forms a layer of unreactive AlO on surface, 2-3nm thick that doesn't flake away

Question 27

What are alloys of Al used for

Answer 27

Low density

Question 28

Cu + Tin

Answer 28

Bronze

Question 29

Cu + Zinc

Answer 29

Brass

Question 30

Nitinol

Answer 30

Memory alloy reforms og shape when heated and cooled

Question 31

24 karats

Answer 31

100% gold

Question 32

12 karats

Answer 32

50% gold

Question 33

Why is gold alloyed

Answer 33

Hardness Colour Cheap

Question 34

Composites

Answer 34

Reinforcement Matrix Reinforcement provides strength Matrix surrounds and holds reinforcement in place

Question 35

Ceramics

Answer 35

Shaping wet clay and heating in furnace Forms cross links in a giant covalent structure

Question 36

Soda-lime glass

Answer 36

Sand limestone sodium carbonate

Question 37

Borosilicate

Answer 37

Sand and boron trioxide Higher melting point

Question 38

Glass structure

Answer 38

Giant covalent

Question 39

Melting point in polymers

Answer 39

Strength of IM forces holding polymer chains together Longer chain = stronger forces Monomer used also affects strength of IM forces

Question 40

Polyethene reaction conditions

Answer 40

HDPE LDPE

Question 41

Thermosoftening polymer

Answer 41

Melts No cross links

Question 42

Haber process

Answer 42

Methane = Natural gas Methane + steam -> Hydrogen + Carbon monoxide Hydrogen + oxygen = water [removes o2 from air to leave N] Nitrogen + Hydrogen -> Ammonia N2 (g) + 3H2 (g) -> 2NH3 (g)

Question 43

Conditions for haber

Answer 43

450 degrees 200 atmospheres Iron catalyst

Question 44

What does condensing ammonia do

Answer 44

Unused reactant gases separated from ammonia easily and recycled into reactor Equilibrium position shifts to right as product is removed

Question 45

NPK fertiliser

Answer 45

Formulation and contains carefully measured salt quantities

Question 46

Nitrogen

Answer 46

Amino caids/proteins

Question 47

Phosphorous

Answer 47

DNA, root growth, flower production

Question 48

Potassium

Answer 48

Growth and crop yield

Question 49

Why is manure not used

Answer 49

Parasites

Question 50

Where does nitrogen come from in NPK

Answer 50

Haber

Question 51

Where does ammonium nitrate come from

Answer 51

Nitric acid + Ammonia -> Ammonium nitrate HNO3 + NH3 -> NH4NO3

Question 52

Potassium salts

Answer 52

Mined

Question 53

Phosphorous

Answer 53

Extracted from phosphate rock

Question 54

Phosphate rock and H2SO4

Answer 54

Monocalcium phosphate Calcium sulfate

Question 55

Phosphate rock and HNO3

Answer 55

Phosphoric acid Calcium nitrate

Question 56

Phosphate rock and H3O4P

Answer 56

Calcium phosphate

Question 57

HDPE

Answer 57

High density Higher melting point

Question 58

LDPE

Answer 58

Low density Lower melting point