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BMAT Additional Content > Chemistry > Flashcards

Chemistry Flashcards

1
Q

Who showed that the plum pudding model was wrong and how?

A
  • Ernest Rutherford
  • Using the gold foil experiment.
  • They fired positively charged particles at a very thin sheet of gold, expecting most of them to be deflected. In reality, very few were.
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2
Q

What came as a result of the gold foil experiment?

A

Rutherford suggested the nuclear model of the atom, with a positive nucleus and a cloud of electrons around it.

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3
Q

Who refined the nuclear model of the atom proposed by Rutherford and how?

A
  • Niels Bohr
  • He suggested that the electrons were not in a cloud (which would cause the atom to collapse), but in shells with defined energies.
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4
Q

How is copper extracted from its ore?

A

• Copper is displaced from copper sulphate by reacting it with iron.
OR
• Copper is extracted from its ore by heating with carbon, then electrolysis to purify the product.

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5
Q

Are the first 3 alcohols soluble?

A

Yes, they dissolve in water to give a neutral solution.

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6
Q

What is produced when an alcohol reacts with sodium?

A

Alkoxide + Hydrogen

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7
Q

C2H5OH + Na ->

A

2C2H5OH + 2Na -> 2C2H5ONa + H2

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8
Q

Name: C2H5ONa

A

Sodium ethoxide (an alkoxide)

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9
Q

What are some uses of alcohols?

A
  • Solvent -> Dissolves most things that water does, plus hydrocarbons, etc.
  • Fuel
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10
Q

What is produced when a carboxylic acid reacts with a carbonate?

A
  • Salt
  • Carbon dioxide
  • Water
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11
Q

What are the name endings for the salts produced by carboxylic acid reactions?

A
  • oates

e. g. sodium ethanoate

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12
Q

Ethanoic acid + Sodium carbonate ->

A

Ethanoic acid + Sodium carbonate -> Sodium ethanoate + Carbon dioxide + Water

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13
Q

Give some examples of common carboxylic acids.

A
  • Citric acid

* Ethanoic acid (vinegar)

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14
Q

How can ethanoic acid be produced?

A
  • Oxidising ethanol using microbes (like yeast).

* Ethanol + Oxygen -> Ethanoic acid + Water

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15
Q

Give a use of ethanoic acid.

A
  • Vinegar (when dissolved in water)

* Solvent (although it makes the solution acidic)

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16
Q

Give a use of citric acid.

A
  • Fizzy drinks

* Scale removal

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17
Q

Give some general uses of carboxylic acids.

A
  • Soap

* Preparations of esters

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18
Q

Give the state and colour of flourine.

A

Yellow gas

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19
Q

Give the state and colour of chlorine.

A

Green gas

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20
Q

Give the state and colour of bromine.

A

Red-brown liquid

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21
Q

Give the state and colour of iodine.

A

Dark grey solid

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22
Q

Give some uses of argon.

A
  • Inert atmosphere in lightbulbs

* Protection for metals being welded

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23
Q

Give some uses of helium.

A
  • Party balloons

* Airships

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24
Q

What is another name for a giant covalent structure?

A

Macromolecule

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25
Q

What are some uses of transition metals?

A

Usually used as catalysts.

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26
Q

What do compounds of transition metals usually look like?

A

Colourful

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27
Q

Remember to revise the hazard symbols.

A

Pg 137.

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28
Q

What is the difference between acid strength and acid concentration?

A
  • Acid strength - The proportion of acid molecules that ionise in water.
  • Acid concentration - How many moles of acid there are per volume of water.
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29
Q

What is a better conductor: strong or weak acid?

A

Strong acid

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30
Q

What does the electrolysis of an acid produce?

A

Hydrogen gas

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31
Q

How can you test for some metal ions without a flame test?

A
  • Add NaOH
  • Look for a coloured precipitate (metal hydroxide)
  • The colour identifies the metal ion
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32
Q

What colour is calcium hydroxide? (Ca2+)

A

White

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33
Q

What colour is copper hydroxide? (Cu2+)

A

Blue

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34
Q

What colour is iron(II) hydroxide? (Fe2+)

A

Green

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35
Q

What colour is iron(III) hydroxide? (Fe3+)

A

Brown

36
Q

What colour is aluminium hydroxide? (Al3+)

A

White

NB: redissolves in excess NaOH though

37
Q

What colour is magnesium hydroxide? (Mg2+)

A

White

38
Q

In metal ion precipitation tests, how can you tell apart aluminium hydroxide from the other white precipitates?

A

Aluminium hydroxide redissolves in excess NaOH to give a colourless solution.

39
Q

What are the two phases of chromatography?

A
  • Mobile phase

* Stationary phase

40
Q

Explain the concept of phases in chromatography.

A
  • The mobile phase is usually a liquid or gas in which the molecules of the substance can move.
  • The stationary phase is usually a solid in which the molecules of the substance cannot move.
  • Molecules of the substance can move between phases until they reach an equilibrium -> The position depends on the solubility of the substance in that solvent.
41
Q

Give an example of the mobile and stationary phase.

A
  • Mobile - Solvent such as ethanol

* Stationary - Paper

42
Q

Describe paper chromatography in detail.

A

1) A spot of the substance is placed on a baseline on the paper (stationary phase).
2) This is placed in a beaker with solvent (mobile phase).
3) Solvent moves up the paper.
4) The chemicals in the substance dissolve in the solvent. This sets up an equilibrium between the phases.
5) When a molecule is in the mobile phase, it moves up with the solvent.
6) So the more time a chemical spends in the mobile phase, the further up the paper it will travel.
7) Before the solvent reaches the top of the paper, it is removed from the beaker.

43
Q

What things can affect how long a chemical spends in the mobile phase?

A
  • Solubility in the solvent

* Attraction to the stationary phase (e.g. paper)

44
Q

Name two types of chromatography.

A
  • Paper chromatography

* Thin-layer chromatography (TLC)

45
Q

What is TLC chromatography?

A
  • Thin-layer chromatography
  • It is like paper chromatography, but the stationary solvent is a thin layer of solid (e.g. silica gel spread on a plate)
  • The mobile phase is a solvent, just like in paper chromatography
46
Q

How can the purity of an isolated substance be improved?

A

Repeating the isolation process (e.g. filtration, evaporation, crystallisation)

47
Q

Give 2 examples when the purity of an isolated substance is important.

A

1) Pharmaceuticals - Impurities could do humans harm

2) Petrochemicals - Impurities could do engine damage

48
Q

Describe how you can calculate the purity of an isolated substance.

A

1) Do a titration to work out the mass of the pure isolated substance that must be reacting.
2) Compare this to the actual mass of the impure isolated substance.
3) Work out a percentage purity.

49
Q

What is electroplating?

A

The use of electrolysis to coat the surface of a metal with another metal.

50
Q

Describe how electroplating works.

A
  • Negative electrode is the object to be coated, while positive electrode is the pure metal to coat it with. Electrolyte must also contain the plating metal.
  • This forms an electrolysis circuit.
  • This causes the plating metal to lose electrons, travel across the chamber, gain electrons at the negative electrode and be deposited there.
51
Q

What is each electrode made of in electroplating?

A
  • Negative electrode (cathode) -> Object to be coated

* Positive electrode (anode) -> Plating metal

52
Q

Explain how you could electroplate a brass cup in silver.

A
  • Make the brass cup the negative electrode
  • Make a piece of silver the positive electrode
  • Make a silver nitrate solution the electrolyte
53
Q

Explain how you could electroplate a metal in copper.

A
  • Make the metal the negative electrode
  • Make a piece of copper the positive electrode
  • Make a copper sulphate solution the electrolyte
54
Q

What is hardness of water?

A

The amount of dissolved calcium and magnesium in water.

55
Q

What are the main problems of hard water?

A
  • Scum

* Scale

56
Q

Explain how hard water leads to scum and why this is a problem.

A
  • Magnesium and calcium in the water react with the soap to give scum
  • This scum is insoluble
  • Therefore, more soap has to be used to get a good lather, which is expensive
57
Q

Explain how hard water leads to scale and why this is a problem.

A
  • Boiling hard water leads to the deposition of scale in pipes, kettles and boilers.
  • This reduces the efficiency of these devices and can block them.
58
Q

What is scale?

A

Mostly calcium carbonate

59
Q

How does scale affect devices?

A
  • Scale can block pipes

* Scale is a thermal insulator, so it can reduce the efficiency of heating devices

60
Q

What ions tend to cause hard water?

A

Ca2+ and Mg2+

61
Q

Describe how hard water can be formed.

A

Rain falling on certain rocks can dissolve compounds like:
• Calcium sulfate
• Magnesium sulfate

62
Q

Give 2 benefits of hard water.

A
  • Ca2+ ions are good for strong teeth and bones

* Minerals in the water may reduce the risk of heart disease

63
Q

What are the two types of water hardness?

A
  • Temporary

* Permanent

64
Q

What is temporary hardness caused by?

A

Hydrogencarbonate ions HCO3- in Ca(HCO3)2

65
Q

What is permanent hardness caused by?

A

Dissolved calcium sulphate (amongst other things)

66
Q

How can temporary hardness of water be removed?

A
  • Boiling -> Calcium hydrogencarbonate decomposes to insoluble calcium carbonate
  • Add washing soda (sodium carbonate) -> Carbonate ions react with Ca2+ to give insoluble CaCO3
  • Ion exchange column -> Sodium or hydrogen ions are exchanged for the Ca2+ ions
67
Q

How can permanent hardness of water be removed?

A
  • Add washing soda (sodium carbonate) -> Carbonate ions react with Ca2+ to give insoluble CaCO3
  • Ion exchange column -> Sodium or hydrogen ions are exchanged for the Ca2+ ions
68
Q

What two methods of removing hardness of water work for both temporary and permanent hardness?

A
  • Add washing soda (sodium carbonate) -> Carbonate ions react with Ca2+ to give insoluble CaCO3
  • Ion exchange column -> Sodium or hydrogen ions are exchanged for the Ca2+ ions
69
Q

Explain how boiling water can be used to remove temporary hardness.

A
  • Calcium hydrogencarbonate decomposes into insoluble calcium carbonate, which forms solid limestone, leaving no ions in the water
  • Calcium hydrogencarbonate -> Calcium carbonate + Carbon dioxide + Water
  • Ca(HCO3)2 -> CaCO3 + CO2 + H2O
70
Q

What is the limescale on your kettle and what causes it?

A

Calcium carbonate, deposited when temporarily hard water is boiled.

71
Q

Why can permanent hardness of water not be removed by boiling?

A

Calcium sulphate does not decompose easily on heating.

72
Q

Explain how adding washing soda can be used to remove hardness of water.

A
  • Carbonate ions in the washing soda (sodium carbonate) react with Ca2+ and Mg2+ ions in the water, which causes an insoluble solid to form
  • Ca2+ + CO3 2- -> CaCO3
73
Q

Explain how an ion exchange column can be used to remove hardness of water.

A
  • Column has lots of sodium or hydrogen ions, which can be used to ‘exchange’ calcium or magnesium in the water
  • Na2(Resin) + Ca2+ -> Ca(Resin) + 2Na+
74
Q

Describe an experiment to compare the hardness of several samples of water.

A
  • Put 50cm3 of soap solution in a burette
  • Put 50cm3 of the first water sample in a flask
  • Keep adding 1cm3 of the soap solution to the water and then shaking to try and get a good lather
  • Do this until the bubbles on the surface stay for at least 30 seconds
  • Record this volume of soap and then repeat with all the different water samples, both boiled and not boiled
75
Q

Is the reaction between hydrogen and water exothermic or endothermic?

A

Exothermic

76
Q

Describe the energy level diagram for hydrogen reacting with water.

A
  • Starting line with H2 and O2
  • Middle line above the starting line with H and O
  • End line below the starting line with H2O
77
Q

What is a fuel cell?

A

An electrical cell that’s supplied with oxygen and fuel, which it uses to produce electrical energy.

78
Q

Give an example of a fuel cell.

A

A hydrogen-oxygen fuel cell.

79
Q

What does a hydrogen-oxygen fuel cell produce?

A
  • Heat energy

* Water

80
Q

What is the advantage of a hydrogen-oxygen fuel cell?

A

It does not produce any pollutants.

81
Q

What type of reaction does a hydrogen-oxygen fuel cell involve?

A

Redox

82
Q

Describe how a hydrogen-oxygen fuel cell works.

A

1) Electrolyte is potassium hydroxide
2) Hydrogen goes into anode compartment and anode goes into cathode compartment
3) At the cathode, oxygen gains electrons and reacts with the water in the electrolyte to make OH- ions
O2 + 4e- + 2H2O -> 4OH-
4) At the anode, the hydrogen reacts with the OH- to give water and electrons
2H2 + 4OH- -> 2H2O + 4e-
5) Current flows through an external circuit from anode to cathode

83
Q

What is the overall equation for the reaction in a hydrogen-oxygen fuel cell?

A

2H2 + O2 -> H2O

84
Q

What happens at the anode in a hydrogen-oxygen fuel cell?

A
  • Hydrogen is oxidised by losing electrons
  • Then it combines with OH- ions to give water and electrons
  • 2H2 + 4OH- -> 2H2O + 4e-
85
Q

What happens at the cathode in a hydrogen-oxygen fuel cell?

A
  • Oxygen is reduced by gaining electrons
  • Then it reacts with water (from the electrolyte) to make OH- ions
  • O2 + 4e- + 2H2O -> 4OH-
86
Q

Give half and overall equations for what is happening in a hydrogen-oxygen fuel cell.

A

Cathode: O2 + 4e- + 2H2O -> 4OH-
Anode: 2H2 + 4OH- -> 2H2O + 4e-
Overall: 2H2 + O2 -> H2O

87
Q

Remember to revise the diagram for the hydrogen-oxygen fuel cell.

A

Pg 188.

BMAT Additional Content (5 decks)

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