Topic 5

Question 1

What type of metal are most metals?

Answer 1

Transition metals

Question 2

What are the typical properties of transition metals and their compounds?

Answer 2

1. high melting point
2. High densities
3. They form coloured compounds
4. They make good catalysts

Question 3

What is the catalyst used in the Haber process to make ammonia?

Answer 3

Iron

Question 4

What is oxidation?

Answer 4

When a metal loses electrons

Question 5

The oxidations of metals results in ….

Answer 5

corrosion

Question 6

What is rusting and when can it only happen?

Answer 6

Rusting is the name for the corrosion and iron and it can only take place with both oxygen and water

Question 7

Give 3 examples of preventing rusting by coating iron with a barrier to keep out water, oxygen or both?

Answer 7

1. Painting - ideal for large and small structures
2. Oiling or greasing - when moving parts are involved
3. Galvanising - coating iron with zinc and the zinc will corrode instead of iron as zinc is more reactive (the zinc also acts as a barrier)

Question 8

What is electroplating and give examples of objects that can be electroplated?

Answer 8

coating the surface of a metal with another metal using electrolysis

e.g. household objects like cutlery and cooking utensils

Question 9

What is the cathode when using electrolysis for electroplating?

Answer 9

The object you’re going to electroplate

Question 10

What is the anode when using electrolysis for electroplating?

Answer 10

The bar of metal you’re using for the plating

Question 11

What is the electrolyte when using electrolysis for electroplating?

Answer 11

a solution containing the metal ions of the metal you’re plating

Question 12

Why are alloys strong?

Answer 12

Different elements have different sized atoms so e.g. carbons small atoms will upset layers of pure iron atoms, making it more difficult for the layers to slide over each other

Question 13

Why is iron alloyed with other metals to produce steels?

Answer 13

1 - Steel is harder and stronger than iron (as carbon is added)
2 - steel is much less likely to rust than iron

Question 14

Describe the properties and uses of bronze

Answer 14

-Bronze = copper + tin

• harder than copper
• used to make medals/ornaments

Question 15

Describe the properties and uses of brass

Answer 15

Brass = Copper + zinc

• more malleable than bronze
• used in situations where lower friction is needed e.g. water taps and door fittings

Question 16

Describe the properties and uses of gold alloys

Answer 16

• Gold can be added with materials such as silver to strengthen it as gold is soft and malleable

Question 17

Describe the properties and aluminium alloys

Answer 17

• stronger than pure aluminium

- aluminium has a low density so it is suitable in aircrafts

Question 18

Describe the properties and uses of magnalium

Answer 18

Magnalium = magnesium + aluminium

• its stronger, lighter and corrodes less easily than pure aluminium
• more stable than pure magnesium
• can be used in fireworks because of reactivity (magnesium)

Question 19

What is the formula for conc that is relates to moles and volume?

Answer 19

Conc = moles/ volume

Question 20

How do you convert mol dm 3 into g dm 3?

Answer 20

by multiplying the concentration of a solution in mol d3 by the relative formula mass of the solute

Question 21

Describe how you would use titrations to find out concentrations?

Answer 21

1. Using a pipette, measure out a set volume of alkali into a flask.Add a few drops of indicator e.g phenolpthalein
2. Fill a burette with a known conc of acid
3. Use burette to add acid to alkali a bit at a time and swirl flask regularly. Go slowly when alkalis almost neutralised (use rough titrations first)
4. Indicator changes colour when all alkali is neutralised
5. Record the volume of acid used to neutralise the acid
6. repeat this process a few times and then take a mean with similar results

Question 22

What is the formula to work out Percentage yield?

Answer 22

Percentage yield = actual yield/theoretical yield * 100

Question 23

Why is the actual yield usually less than the theoretical yield?

Answer 23

1. Incomplete reactions - If not all of the reactants are converted to products, yield will be lower than expected
2. Practical losses - may lose reactants when you transfer chemicals between containers
3. Unwanted reactions - If unexpected reactions happen, the yield of the intended product goes down. These can be caused my impurities in the reactants, or sometimes by changes to the reaction conditions

Question 24

What is atom economy?

Answer 24

The % of reactants changed to useful products

Question 25

What is the formula for atom economy?

Answer 25

Atom economy = (total mr of desired products/ total mr of all products) * 100

Question 26

what are the cons of reactions with a low atom economy

Answer 26

1- They use up resources quickly but make lots of waste materials that have to be disposed of. This tends to make the reactions unsustainable 2- They aren't profitable as raw materials can be expensive to buy and waste products can be expensive to remove

Question 27

What could you do to reverse the negative effects of reactions with low atom economy?

Answer 27

Find a use for the waste products rather than just throwing them away

Question 28

what 3 other factors are considered in industry (apart from atom economy)

Answer 28

1- Percentage yield of reaction - the higher the yield, the better 2. Rate of reaction - Rate must be fast enough to produce the amount of product you need in a sensible amount 3. If reaction is reversible - to keep yield of a reversible reaction high, you may need to alter the equilibrium position by changing reaction conditions (expensive)

Question 29

Define molar volume?

Answer 29

The volume occupied by one mole of gas

Question 30

What is the formula for molar volume? (not in same conditions)

Answer 30

molar volume = gas volume/number of moles

Question 31

What is the formula to work out volume? (under same conditions)

Answer 31

volume = moles * 24

Question 32

What factors are considered when designing an industrial process?

Answer 32

1. The cost of extracting and refining raw materials 2. Energy costs - (maintaining temperature and pressure) 3. The ability to control the conditions - maximising yield but keeping the reaction running at an acceptable rate

Question 33

What is the equation for producing ammonia in the Haber Process?

Answer 33

N2(g) + 3H2 ------ 2NH3(g) (+heat) ------ = reversible reaction

Question 34

Explain the conditions used in the Haber Process?

Answer 34

1. Higher pressures favour the forward reaction as theres 4 moles of gas on LHS, for every 2 on RHS) 2. Pressure it set as high as possible (200 up atmospheres) to give the best yield without making plant too expensive to build 3. Forward reaction is exothermic which means increasing the temp will move equilibrium position the wrong way - away from ammonia and towards N2 and H2, so yield of ammonia is greater at lower temps 4. Industry still use high temps to increase reaction rate

Question 35

What affects how quickly equilibrium is reached?

Answer 35

- Temp, pressure and concentration (equilibrium is always reaches faster using high temp, pressure, and conc) - Catalysts (e.g. iron) makes reactions go faster, so it reaches equilibrium faster (but it doesnt affect anything else) -

Question 36

Describe the Haber Process?

Answer 36

1. Hydrogen and Nitrogen are mixed in a 3:1 ratio 2. Combined in a reaction vessel containing trays of iron catalysts (at 450 degrees and 200 atm) 3. A condenser cools the N2 and H2 to produce ammonia 4. The unused N2 and H2 are recycled

Question 37

What do fertilisers contain that promotes plant growth?

Answer 37

1. Nitrogen 2. Phosphorus 3. Potassium

Question 38

Ammonia can be reacted with oxygen and water to make...

Answer 38

nitric acid

Question 39

Ammonia and nitric acid react together to produce the salt...

Answer 39

Ammonium nitrate (NH3 (aq) + HNO3(aq) ____NH4NO3

Question 40

Describe how to make ammonium sulfate in a lab with ammonia and dilute sulfuric acid?

Answer 40

1) add a few drops of methyl orange to ammonia - itll turn yellow 2) Slowly add dilute sulfuric acid from the burette into ammonia until yellow just changes red (acid). Swirl flash as acid is added 3) To make ammonium sulfate pure, note how much sulfuric acid it took to neutralise ammonia and repeat titration using that volume of acid but no indicator 4) To get crystals, evaporate half of the solution and leave to crystalise. Filter out the crystals and leave them to dry

Question 41

Why cant you use titrations to create ammonium sulfate in industry?

Answer 41

Impractical to use burettes and steam baths for large quantities

Question 42

What other methods could you use to ceate ammonium sulfate in industry?

Answer 42

1. You could produce ammonia with the Haber Process and produce sulfuric acid in the 'contact process' (you dont need to know what this is) 2. Use a large chamber filled with ammonia gas and spray sulfuric acid into the chamber to produce ammonium sulfate powder

Question 43

Chemical cells produce a voltage across the cell until....

Answer 43

all of one of the reactants is used up

Question 44

What is a fuel cell?

Answer 44

An electrical cell that's supplied with a fuel and oxygen and uses energy from the reaction between them to produce electrical energy efficiently

Question 45

What happens in a hydrogen and oxygen fuel cell?

Answer 45

A voltage is produced by reacting hydrogen and oxygen and water is the only product 2H2 + O2 ___ 2H20

Question 46

What are the advantages of hydrogen-oxygen fuel cells?

Answer 46

1. theyre more efficient than power stations or batteries 2. Electricity is generated directly from the reaction without needing turbines/generators 3. There are no moving parts like in a power station so energy isnt lost through friction 4. Fuel cell vehicles dont produce greenhouses gases, nitrogen oxides or sulfur dioxide. (only steam and water)

Question 47

What are the weaknesses of hydrogen-oxygen fuel cells?

Answer 47

1. Hydrogen is a gas so it takes up more space to store than liquid fuels such s petrol 2. It's explosive so it's difficult to store safely 3. H2 is often made from hydrocarbons or by electrolysis of water. This requires electricity (most likely from fossil fuels)