Topic 5

Question 1

List typical properties of transition metals

Answer 1

• high melting point
• high density
• formation of coloured compounds
• catalytic activity of metals and their compounds as exemplified by iron

Question 2

What does oxidation of metals result in

Answer 2

Corrosion

Question 3

Explain how rusting is iron can be prevented by coating iron with a barrier

Answer 3

This keeps out of water, oxygen or both eg. Painting, piling or greasing

Question 4

Explain how rusting I’d iron can be prevented by sacrificial protection

Answer 4

Involves placing a more reactive metal with the iron. Water and oxygen react with this ‘sacrificial’ metal instead of object your protecting

Question 5

Formula for calculating molar volume

Answer 5

Volume (dm^3)
————————————
Moles X molars volume (24 at room temp)

Question 6

Recall what the the atom economy of reaction tells you

Answer 6

What percentage of the mass of reactants has been converted into desired product when manufacturing chemical

Question 7

Recall calculation for atom economy

Answer 7

Total Mr of desired products
————————————. X100
Total Mr of all products

Question 8

Recall how to calculate percentage yield of a reaction

Answer 8

Actual yield
———————— X100
Theoretical yield

Question 9

Describe how to convert concentration in g dm^-3 into mol dm^-3

Answer 9

conc g dm^-3
———————————
Mr of solute x conc mol dm^-3

Question 10

How to calculate concentration

Answer 10

n
————
C x V

Question 11

what is electroplating and how can it be used

Answer 11

it’s coating surface of metal with another metal using electrolysis

• improves appearance
• improves resistance to corrosion of metal objects

Question 12

why does converting pure metals into alloys often increases the strength of the product

Answer 12

because the different elements have different sized atoms , causing an irregular arrangement of atoms so harder for layers to slide over each other

Question 13

explain why iron is alloyed with other metals to produce alloy steels

Answer 13

steels made by adding small amount of carbon to iron. iron on its own will rust (corrode) fairly quickly, but steel is much less likely to rust

Question 14

bronze

Answer 14

copper + tin , medals,decorative ornaments and statues

Question 15

brass

Answer 15

copper + zinc, water taps and door fittings

Question 16

gold alloys

Answer 16

pure gold very soft and malleable, described as 24 carat. zinc, copper, and silver used to strengthen gold

Question 17

magnallium

Answer 17

aluminium + magnesium, parts of cars and aeroplanes

Question 18

describe the Haber process

Answer 18

a reversible reaction between nitrogen and hydrogen to form ammonia

Question 19

explain how an incomplete reaction can result in the actual yield of a reaction being less than the theoretical yield

Answer 19

if not all reactants converted to product, reaction is incomplete and yield will be lower than expected

Question 20

explain how practical losses can result in the actual yield of a reaction being less than the theoretical yield

Answer 20

always lose a bit when you transfer chemicals between containers

Question 21

explain how an unwanted reaction can result in the actual yield of a reaction being less than the theoretical yield

Answer 21

if unexpected reactions happen, yield of intended product goes down, can be caused by impurities i reactants or sometimes by changes to reaction conditions

Question 22

describe the molar volume of any gas at room temperature and pressure

Answer 22

the volume occupied by one mole of molecules of any gas at room temperature and pressure (24dm^3)

Question 23

give equation using volume, moles and molar volume

Answer 23

V (dm^3)/ n x mr (24)

Question 24

what might fertilisers contain

Answer 24

nitrogen, phosphorus and potassium compounds to promote plant growth

Question 25

describe how ammonia is used to produce nitrogen-containing compounds

Answer 25

ammonia reacted with oxygen and water in series of reactions to make nitric acid. can also react ammonia with nitric acid to produce salt ammonium nitrate

Question 26

explain how in industrial reactions, including the Haber process conditions used are related to availability and cost of raw materials

Answer 26

cost extracting raw materials will affect whether process is economically viable or not. if raw materials too expensive to source may not be profitable to make product

Question 27

explain how in industrial reactions, including the Haber process conditions used are related to availability and cost of energy supplies

Answer 27

high temperatures and pressures cost more to maintain, so low temps and pressure used wherever possible

Question 28

explain how in industrial reactions, including the Haber process conditions used are related to control of temp, pressure and catalyst

Answer 28

important to control conditions to maximise yield but keep reaction running at an acceptable rate

Question 29

describe a chemical cell

Answer 29

produce a voltage across cell until one of reactants is used up

Question 30

describe a hydrogen-oxygen fuel cell

Answer 30

hydrogen and oxygen react to produce a voltage and water is only product

Question 31

describe advantages of hydrogen-oxygen fuel cell

Answer 31

• efficient
• no pollutants produced
• no moving parts, so energy isn’t lost through friction

Question 32

describe disadvantages of hydrogen-oxygen fuel cell

Answer 32

• hydrogen is a gas so takes up more room
• very explosive so difficult to store safely
• hydrogen fuel often made either from hydrocarbons or electrolysis of water which requires electricity