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OCR gcse ChEMisTry > C6.1 > Flashcards

C6.1 Flashcards

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1
Q

What are the three essential elements for plants

A

Nitrogen, Phosphorus and potassium

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2
Q

Sign of each deficiency

A

Nitrogen - poor growth, yellow leaves
Phosphorus - poor root growth, discoloured leaves
Potassium - poor fruit growth, discoloured leaves

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3
Q

What do fertilisers do

A

They replace the elements used by plants as they grow.

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4
Q

What is the haber process equation

A

N2 + 3H2 −⇀ 2NH3

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5
Q

Where are the raw materials for the Haber process got from

A

Nitrogen from the fractional distillation or liquefaction or air
Hydrogen from the reacting of natural gas with steam

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6
Q

How can potassium sulphate and ammonium sulphate be made in the laboratory

A

H2SO4 + KOH you can perform a titration and add activated charcoal to remove phenolphthalein indicator
NH3 + H2SO4 you can perform a titration on it again and add phenolphthalein again and use charcoal to remove it

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7
Q

What colour is phenolphthalein in acid

A

colourless

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8
Q

Difference between a batch process and continuous process

A

batch process - small amount made
Continuous process - make large amounts and go on all the time

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9
Q

Chosen conditions for the Haber process

A

20 MPa
Temperature of 450 degrees
Iron catalyst

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10
Q

Why are these conditions chosen

A

Hazardous and expensive to choose a very high pressure. High equilibrium yield would not justify additional costs and pressure is chosen as a compromise.
Temperature chosen as it’s low enough to achieve reasonable rate of reaction and a reasonable equilibrium yield and iron catalyst work more efficiently at > 400 degrees.

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11
Q

What three materials are needed to make sulfuric acid

A

Sulfur, air and water

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12
Q

What is stage 1 to make sulfuric acid?

A

Sulfur burns in air producing sulfur dioxide
S + O2 -> SO2

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13
Q

What is stage 2 to make sulfuric acid?

A

Sulfur dioxide burns in air producing sulfur trioxide
2SO2 + O2 <-> 2SO3

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14
Q

Conditions chosen for stage 2

A

It’s a reversible reactions so a pressure of 200 kPA is chosen, a temp of 450 degrees and a vanadium oxide catalyst is chosen. 96% yield in these conditions

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15
Q

What is stage 3 to make sulfur trioxide

A

SO3 + H2O -> H2SO4

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16
Q

What is the precaution taken in step 3 and why

A

The precaution is that the reaction is extremely exothermic and produces a hazardous mist so is done in two steps.
H2SO4 + SO3 -> H2S2O7 (oleum)
H2S2O7 +H2O -> 2H2SO4

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17
Q

What are the two ways ethanol can be produced

A

Ethanol can be produced through fermentation or hydration of ethene

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18
Q

Chemical equation of fermentation and conditions chosen

A

C6H12O6 -> 2CO2 + 2C2H5OH
yeast cells become denatured at high temps and rate of the reaction is low at low temps so 35 degrees is chosen

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19
Q

Is hydration of ethene renewable or non renewable

A

It is non-renewable as ethene is involved

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20
Q

Chemical equation of hydration of ethene and conditions chosen

A

C2H4 + H20 <-> C2H5OH
needs a temperature of 300 degrees, a pressure of 60,000 KPa and a phosphoric acid catalyst

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21
Q

What is an ore

A

An ore is a rock or mineral that contains enough metal to make it economical to extract the metal - value of metal is more than cost of extracting it

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22
Q

What does the method to extract a metal depend on

A

The position of the metal in the reactivity series

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23
Q

How are copper and iron extracted

A

Copper and iron are extracted by the heating of it with carbon or with carbon monoxide

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24
Q

How can copper be extracted from copper sulphide

A

2Cus + 3O2 -> 2CuO +2SO2
2CuO + C -> 2Cu + CO2

Copper oxide is reduced, carbon is oxidised

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25
Q

How is iron extracted from is ore

A

Using a blast furnace

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26
Q

How does a blast furnace work

A

Raw materials are added to the top of the blast furnace:
Iron ore such as haematite contains iron (III) oxide
Coke
Limestone which is used to purify the iron

27
Q

Processes that happen in a blast furnace

A

carbon reduces iron (III) oxide to iron.
Step 1: coke burns in hot air making CO2.
C + O2 -> CO2
Step 2: more coke reduces the CO2 making CO
C + CO2 -> 2CO
Step 3: Carbon monoxide reduces iron oxide to iron at 1500 degrees celsius
3CO + Fe2O3 -> 3CO2 + 2Fe

28
Q

what happens to the products of the blast furnace

A

molten iron trickles down the blast furnace where its impurities are removed using calcium carbonate

29
Q

Processes that occur to purify the iron

A

Calcium carbonate decomposes at high temperatures
CaCO3 -> CaO + CO2
Calcium oxide forms which reacts with silica from sandy impurities to form calcium silicate.
CaO + SiO2 -> CaSiO3
The calcium silicate is then collected as slag which floats on top of the molten iron.

30
Q

How does aluminium exist naturally as

A

Aluminium exists naturally as aluminium oxide Al2O3. It’s found in an ore called Bauxite. It’s more reactive than carbon so it has to be extracted through electrolysis.

31
Q

Why is aluminium oxide dissolved in molten cryolite

A

To reduce the boiling point of aluminium oxide and allowing electrolysis to happen as it’s a liquid.

32
Q

What is the anode and cathode and what are the reactions that occur there

A

The graphite lining acts as the cathode and a series of large graphite blocks as the anode.
Aluminium is produced at the cathode
Oxygen is produced at the anode
Al 3+ + 3e- -> Al - cathode
2O2- -> 2O2 + 4e-

33
Q

what is bio-leaching

A

When bacteria oxidises iron (II) and sulphide ions using the energy transferred. The sulphuric acid produced breaks down copper sulphide ores and other minerals releasing copper (II) ions and other metal ions

34
Q

Advantages and disadvantages of bioleaching

A

It’s cheaper than traditional mining and processing. It allows metals to be extracted from ores that contain too little metal for traditional methods to be profitable. The bacteria occur naturally and don’t release harmful substances.

However, sulphuric acid is produced which is a negative.

35
Q

What is phyto-extraction

A

Phyto-extraction is when plants absorb dissolved ions through their roots. A crop is planted on soil with low grade ore. A complexing agent may be added so plants can absorb metal ions more easily. The plants are harvested and then burnt to produce ash with a high concentration of metal which is then extracted.

36
Q

Advantages and disadvantages of phyto-extraction

A

Is cheaper than traditional mining and processing. It produces less waste and involves smaller energy transfers. It may need replanting and harvesting for several years before available metal is removed from the soil. However, it’s carbon neutral and sustainable.

37
Q

What is an alloy

A

An alloy is a mixture of two or more elements at least one of which is a metal.

38
Q

Different alloys, what they are made from and typical uses

A

Steel - iron, buildings, bridges, cars
Solder - tin and copper, joining electrical components and copper poles
Brass - copper and zinc, musical instruments and coins
Bronze - copper and tin, bells and propellors for ships

39
Q

What is solder and why is it useful

A

Melting point of 227 degrees. Makes it useful for joining electrical components without damaging them. Hot solder in the liquid state flows into faps between and solidifies quickly. Metals are good conductors.

40
Q

What is bronze and why are they useful

A

Alloys are stronger and harder than individual metals they contain. Brass is like this. Copper and zinc atoms are of different sizes and it makes it more difficult for copper atoms to slide over each other.

41
Q

What is brass and why are they useful

A

Brass resists corrosion, it doesn’t conduct electricity very well, making it suitable for pins of electric plugs

42
Q

What is corrosion

A

Corrosion is the reaction of a metal with substances in its surroundings like air and water.

43
Q

How does silver get corroded

A

Silver doesn’t react with the oxygen in the air but does erode in the presence of hydrogen sulphide. It reacts with silver producing a layer of black silver sulphide.

44
Q

What is rusting

A

Rusting is a redox reaction. Iron is oxidised to hydrated iron (III) oxide when it reacts with oxygen and water.
iron + water -> hydrated iron (III) oxide
Rusting can continue until the material has been fully eroded.

45
Q

How to prove rusting

A

One nail in a test tube with boiled water (water + no air)
One nail in a test tube with anhydrous calcium chloride (no water + air)
One nail in a test tube with water and air (rusting present)

46
Q

How to reduce corrosion

A

Many of the methods of rust prevention rely on stopping air and water reaching the surface of the metal:
.Painting .Coating with oil, grease or plastic .Plating with zinc .Plating with tin

47
Q

What is sacrificial protection

A

Sacrificial protection involves a metal that is more reactive than iron, such as magnesium or zinc. As long as the iron or steel object is in contact with it, the more reactive metal corrodes first. This method is useful where painting is difficult.

48
Q

What is metal plating

A

A layer of metal is placed onto an iron or steel object preventing air and water reaching the steel or iron below.

49
Q

What is galvanising

A

Galvanising involves the dipping of the metal object in molten zinc. After it has cooled and solidified the layer of zinc does two things:
1) Stops air and water reaching the iron or steel below
2) Acts as a sacrificial metal so that the object is protected even if the zinc layer is damaged

50
Q

What is tin plating

A

The metal is dipped into molten tin, covering it and protecting it from contact with air and water however it’s less reactive so doesn’t prevent rusting.

51
Q

What are ceramics

A

Ceramics are hard non metallic materials. Brick, china, porcelain and glass are all ceramic materials. Ceramic materials are non metals combined to form giant ionic lattices or giant covalent structures. Properties of ceramics:
. High melting points
. Hard and stiff but brittle
. Poor conductors of electricity and heat
. Unreactive

52
Q

What is used for overhead cables and why

A

Aluminium is used for overhead cables for it as it has a high tensile strength, the lowest density and a good conductivity

53
Q

What is used as electrical insulators

A

Porcelain is the most suitable insulator as it has a good electrical resistance, a good tensile strength and a medium compressive strength.

54
Q

What are composite materials

A

Composite materials are made from two or more materials combined together each with different properties of the materials it contains. For example it may be stronger, less dense or cheaper.

55
Q

What do many composite materials consist of

A

they consist of fibres embedded in polymer resin. The fibres have a low density and tensile strength but are brittle whereas resin is hardwearing but isn’t strong. The composite material is lightweight, strong and hard.

56
Q

What does concrete consist of and properties

A

Concrete is a composite material that consists of aggregate (small stones), sand and cement. When water is added chemical reactions happen binding the ingredients together. Concrete has a high compressive strength useful for foundations. Low tensile strength so beams crack. By embedding steel rods in concrete you get steel reinforced concrete with a high compressive and tensile strength

57
Q

What does plywood consist of and it’s properties

A

Plywood is made up of wood glued together it’s resistant to 90 degree bends and is useful for floors and walls

58
Q

What is a life cycle assessment

A

A life cycle assessment is the impact of making, using and disposing of a manufactured product that should be considered when choosing materials. It includes data about
.Sustainability including the use of raw materials and energy
.Environmental impact, including waste products and pollution
.The lifespan of the product and whether it can be recycled
.Disposal, including how easily materials decompose

59
Q

What happens if objects can’t be recycled

A

Unless they can be recycled most materials and products end up in landfill sites as waste. This is not an efficient use of resources,

60
Q

Reasons to recycles

A

Conserving limited raw materials and energy resources
Reducing the release of harmful substances into the environment
Reducing waste

61
Q

Whether are material should be recycled depends on what factors

A

How costly the waste can be collected and sorted
The amount and type of any by products released by recycling
The cost of recycling compared to landfill or incineration
The amount of energy involved in each stage

62
Q

How does recycling occur

A

Waste materials and products must be collected and transported to a recycling plant. These materials have been previously sorted, but further sorting is done at the plant. It is important to ensure that materials aren’t contaminated by other materials. The waste is then shredded or cut into small pieces ready for processing.

63
Q

How does recycling occur during processing

A

Metals are melted by heating and molten metals are poured into moulds to produce new blocks called ingots
Paper is mixed with water, cleaner and rolled and heated to make new paper
Glass is melted by heating and moulded into new glass objects
Polymers like pol (ethene), PE4 and poly (propene) are melted and formed into new objects

OCR gcse ChEMisTry (16 decks)

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