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Chemistry > C6 > Flashcards

C6 Flashcards

0
Q

What is the name given to the liquid that is broken down during electrolysis?

A

The electrolyte

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1
Q

What is electrolysis?

A

The decomposition of a liquid by passing an electric current through it

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2
Q

Which ions discharge the negative cathode and which ions discharge the positive anode?

A

Cations move towards cathode

Anions move towards anode

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3
Q

Water contains small concentrations of hydrogen ions and hydroxide ions, which one discharges at which electrode?

A

Hydrogen discharges at negative cathode

Hydroxide at positive anode

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4
Q

What is the equation for the electrolysis of water at the cathode and the anode?

A

Cathode: 2H+ + 2e- -> H2

Anode: 4OH- - 4e- -> O2 + 2h2O

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5
Q

Which electrode do metals and non-metals travel to?

A

Metal ions –> negative electrode

Non-metal ions –> positive electrode

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6
Q

Why is the electrolysis of molten liquids hard to do whereas the electrolysis of aqueous solutions quite simple?

A

It is hard for molten liquids because of the high temperatures involved whereas it is quite easy for aqueous solutions because aqueous solutions are just substances dissolved in water.

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7
Q

What is used to simple electrolysis? (In terms of equipment)

A
  • two graphite rods as electrodes
  • beaker full of electrolyte
  • a d.c power supply to provide the potential difference (voltage) for a current to be able to flow through it.
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8
Q

Hat colour solution is formed when you dissolve copper sulfate in water?

A

Blue

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9
Q

Copper is produced at the cathode when copper sulfate is dissolved in water. But what else can be formed at the cathode and when? (Think about reactivity)

A

Hydrogen can be formed when the metal in the solution is more reactive than hydrogen or when there is no metal contained in the solution

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10
Q

The amount of product made during electrolysis is __________ to the current used and the time taken for the process. So if you double either the time or current, the amount of product will _____. If you double both, the amount of product will _____.

A
  • Directly proportional
  • double
  • quadruple
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11
Q

Hydrogen is a very flammable gas. What is formed when it is burned and what type of reaction is it?

A

Water vapour is formed and it is an ectothermic reaction

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12
Q

How does a hydrogen-oxygen fuel cell work?

A

In a hydrogen-oxygen fuel cell hydrogen is used as the fuel. When oxygen or air is supplied the hydrogen and oxygen react together. The energy released is used to produce a potential difference/voltage, causing a current to flow when the fuel cell is connected to a circuit.

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13
Q

What is a redox reaction?

A

When there is a reduction of one substance but oxidation of another substance

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14
Q

In a fuel cell, oxidation happens at the ______ and reduction happens at the ______.

A

Anode

Cathode

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15
Q

What are the advantages of using hydrogen-oxygen fuel cells on spacecraft?

A
  • lightweight
  • compact
  • no moving parts
  • can be used to make drinking water for taro aughts
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16
Q

Hat are the advantages of using hydrogen-oxygen fuel cells to power cars instead of petrol and diesel?

A
  • water vapour Is the only waste product produced
  • no carbon dioxide released
  • there is a potential large supply of hydrogen due to the electrolysis of water
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17
Q

What are the drawbacks of hydrogen-oxygen fuel cells?

A
  • most of hydrogen production is from fossil fuels

- fuel cells often contain poisonous catalysts which have it disposed of properly at the end of the fuel cells life

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18
Q

As well as being the gain or loss of electrons from a substance, what is oxidation and reduction?

A

When a substance gains oxygen (oxidation). When a substance loses oxygen (reduction).

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19
Q

What is a oxidising agent?

A

A substance that removes electrons from another substance

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20
Q

What is a reducing agent?

A

A substance that adds electrons to another substance

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21
Q

Cast iron contains about 4% carbon. This makes it hard and too brittle for most uses. However the carbon stops the iron from rusting, how does it do this?

A

The carbon reacts to form insoluble products that stop water and air from reaching the metal.

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22
Q

How is rusting an example of a redox reaction?

A

Because the iron atoms are oxidised to form iron(III) ions. And oxygen atoms are reduced to oxide ions

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23
Q

What is rust?

A

Hydrated iron(III) oxide

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24
Q

Name 4 different methods of preventing rusting

A
  • painting
  • oiling
  • plating with tin
  • plating with zinc (galvanising)
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25
Q

How is stainless steel resistant to rusting?

A

It contains chromium, which when exposed to air, reacts to form chromium oxide that forms a thin layer on top of the steel, stopping air and water from getting to the metal below

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26
Q

How/why does galvanising work?

A

You galvanise something by plating it with a metal that is more reactive than the metal it is protecting. The more reactive metal loses electrons much more easily an so it is more readily oxides, so it sort of sacrifices itself to protect the metal below

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27
Q

How iron rust quicker if the TIN plating is broken?

A

Because tin is not more reactive than iron and so is not as readily oxidised

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28
Q

What is the name of the alcohol that alcoholic drinks contain?

A

Ethanol

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29
Q

Ethanol is just 1 in a family of similar substances, what atoms are theses substances made out of?

A

Hydrogen, carbon and oxygen

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30
Q

Other than alcohol, what can ethanol be used for?

A
  • fuel for cars

- a solvent in aftershave and perfumes

31
Q

What is fermentation?

A

A method of making ethanol

32
Q

Fermentation relies on a fungi called yeast. What role does yeast play in the fermentation process?

A

Yeast contains enzymes that convert glucose into carbon dioxide and ethanol

33
Q

How is ethanol extracted from fermentation?

A

Via fractional distillation

34
Q

During fermentation, why does the temperature have to be kept between 25 - 50°c and why can oxygen not get in?

A

Hast to be above 25°c because yeast are living organisms and will become inactive below that temperature, but cannot go above 50°c because the enzymes inside the yeast would denature. Oxygen cannot get in either because it would cause the ethanol to oxidise to Ethanoic acid.

35
Q

How else other than fermentation can your make ethanol?

A

You can make ethanol through a hydration reaction

36
Q

What is the difference between fermentation and hydration?

A

Fermentation uses glucose from pants etc. and so is renewable. Whereas the ethane needed for a hydration reaction comes from cracking crude oil fractions?

37
Q

What is the equation for the hydration reaction for making ethanol?

A

Ethane + water -> ethanol

38
Q

What are the advantages and disadvantages of using a fermentation process instead of hydration process?

A

Advantages

  • renewable
  • requires very little energy

Disadvantages

  • low atom economy
  • low percentage yield
  • low purity
  • batch process so it is more labour intensive
39
Q

What is the general formula for the molecular formula of alcohols? Ethanol is c2h5OH

A

C H OH

n 2n+1

40
Q

What is ozone?

A

It is a form of oxygen with the formula O3

41
Q

Ozone is found throughout the whole atmosphere, but where is it the most concentrated?

A

In the stratosphere

42
Q

Where is the stratosphere found?

A

10km -50km above the earths surface

43
Q

What happens when ultraviolet comes into contact with oxygen?

A

It causes it to react forming ozone

44
Q

What atoms are CFCs made up of?

A
  • carbon
  • chlorine
  • fluorine
45
Q

How do CFCs damage the ozone layer?

A

CFCS molecules spread out in the atmosphere after they are released. The ultra violet in the stratosphere breaks the Bonds between the carbon and chlorine atoms are broken, releasing chlorine radicals (highly reactive chlorine atoms). These chlorine radicals react with the ozone molecules and break them down into oxygen, this reaction produces chlorine atoms so even more ozone molecules are broken down. (Chain reaction)

46
Q

There are many different types of CFCs, but they all have similar properties. Name 3

A
  • chemically inert (don’t react easily with other substances)
  • insoluble in water
  • have low boiling points and so are usually gases
47
Q

How many ozone molecules does 1 chlorine molecule break?

A

100000

48
Q

What are the alternatives to CFCs?

A
  • alkanes

- HFCs

49
Q

What atoms make up a HFC?

A
  • hydrogen
  • fluorine
  • carbon
50
Q

Which water is better for lathering soap. Hard water or soft water?

A

Soft water

51
Q

Hard water contains ____ concentrations of magnesium and calcium ions. Soft water contains ____ concentrations

A
  • high

- low

52
Q

Why does acid rain corrode limestone and chalk?

A

Limestone and chalk are made up of mainly calcium carbonate, which reacts with acid rain (carbon dioxide and water) to form calcium hydrogen carbonate, which is soluble in water.

53
Q

What does the hardness of water depend on?

A

The type of rocks the water as flowed over and through.

54
Q

There are 2 types of water hardness. What are the two caused by each?

A

Permanent hardness is caused by dissolved calcium sulfate

Temporary hardness is caused by dissolved calcium hydrogencarbonate

55
Q

What is the difference between permanent hardness and temporary hardness?

A

Temporary water hardness can be removed by boiling it whereas permanent water hardness cannot. This is because calcium hydrogen carbonate decomposes when heated.

56
Q

What substance can be used to remove both temporary and permanent hard water?

A

Sodium carbonate (washing soda)

57
Q

How does washing soda soften hard water?

A

Sodium carbonate is soluble in water and when it is added to water a precipitation reaction occurs. The calcium and magnesium ions are removed as a precipitate.

58
Q

Name another method of removing water hardness other than washing soda

A

Ion exchange columns

59
Q

What do ion exchange columns contain?

A

Ion exchange resins

60
Q

What type of ions of ion exchange resins contain?

A

Sodium ions

62
Q

How is the resin regenerated?

A

Sodium chloride solution is poured down the column which swaps sodium ions back ingot the resin while pushing the calcium and magnesium ions out and are washed away in waste water.

63
Q

How does testing for un saturation work?

A

The bromine water reacts with the carbon-carbon double bonds in unsaturated compounds. Here an addition reaction takes place and a colourless dibromo compound is made.

64
Q

What does it mean if we say two liquids are immiscible?

A

They cannot mix together

65
Q

Is milk an oil in water emulsion or a water in oil emulsion?

A

Oil in water emulsion. Small drops of butterfat are mixed in with liquid

66
Q

How does an ion exchange column work?

A

As water passes through it the ion exchange resins swap the ions in the water for the ions in the resin. The water becomes soft because the calcium and magnesium ions are removed.

67
Q

Margarine is a water in oil emulsion and is made up of a mixture of different vegetable oils. Unsaturated vegetable oils have low melting points, so how is the correct consistency for marguerite achieved?

A

By mixing it with saturated vegetable oils

68
Q

How are unsaturated vegetable oils turned into saturate vegetable oils?

A

By reacting then with hydrogen. The hydrogen reacts at the double bonds, turning them into single bonds

69
Q

How is soap made and what is this process called?

A

By reacting fats or oils with hot sodium hydroxide solution. This splits the oils into glycerol and sodium salts, the salts are the soap. This process is called saponification.

70
Q

What type of reaction is saponification?

A

Hydrolysis reaction

71
Q

What is a hydrolysis reaction?

A

Type of reaction where a compound is broken down by its reaction with water

72
Q

What is an advantage of detergents?

A

They form a lather in hard water as well as soft water

73
Q

What are detergents?

A

A substance that can surround the fat and oil molecules in stains and remove them. They are an ingredient in washing up liquids and washing powders.

74
Q

Why are washing powders that contain enzymes called?

A

Biological powders

75
Q

What do enzymes in washing powders do?

A

Remove stains in low temperature washes

Chemistry (4 decks)

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