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Chemistry > C4 - Chemical changes > Flashcards

C4 - Chemical changes Flashcards

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1
Q

What is an ore?

A

Rocks containing enough metal to be worth extracting.

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2
Q

What is electrolysis?

A

Splitting an ionic compound into simpler substances using an electric current.

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3
Q

When do we use electrolysis?

A

When our metal is more reactive than carbon. When are substance contains ions.

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4
Q

What is an electrolyte?

A

Liquid containing ions. Must be able to conduct electricity.

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5
Q

What is a Cathode?

A

Connects to the negative side of the battery (the negative electrode). Attracts cations.

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6
Q

What is an anode?

A

Connects to the positive side of the battery (the positive electrode). Attracts anions.

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7
Q

Why do we melt or dissolve the solution in water?

A

To allow ions to flow.

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8
Q

What does water split into?

A

hydrogen ions (H+) and hydroxide ions (OH-)

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9
Q

What are the positive ions in CuSO4 when it is dissolved in water?

A

Cu(charge)2+ and H+

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10
Q

What are the negative ions formed at the anode in CuSO4 when it is dissolved in water?

A

SO4 (charge)2- and OH-

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11
Q

What is the rule for what forms at the cathode (-)?

A

The less reactive positive ion forms here.

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12
Q

What is the rule for what forms at the anode(+)?

A

Oxygen forms unless a halide ion is present. (Group 7 element)

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13
Q

Why does CO2 form in electrolysis?

A

Oxygen formed from electrolysis reacts with the graphite anode, forming carbon dioxide.

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14
Q

When does a neutralisation reaction occur?

A

When an acid and an alkali react together.

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15
Q

What is the word equation for a neutralisation reaction?

A

Acid + Alkali -> Salt + Water

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16
Q

What do all acids contain?

A

H+ ions

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17
Q

What do all alkalis contain?

A

OH- ions

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18
Q

What determines if an acid or alkali is weak or strong?

A

How ionised it is in water.
Weak acid/alkali - only partially ionised in water
Strong acid/alkali - 100% or fully ionised in water.

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19
Q

What is oxidation?

A

When a substance loses electrons. (gains oxygen)

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20
Q

What is reduction?

A

When a substance gains electrons. (loses oxygen)

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21
Q

What is the reactivity series of metals?

A

Shows the metals in order of reactivity.

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22
Q

What groups react with water?

A

Mostly Group 1 metals and Group 2 metals react with water.

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23
Q

How are metals more reactive than carbon extracted?

A

Electrolysis

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24
Q

Why must an ionic substance have been melted or dissolved in water?

A

So ions are free to move.

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25
Q

What happens in electrolysis?

A

Positively charged ions move to the negative electrode. They gain electrons and are reduced.

Negatively charged ions move to the positive electrode. They lose electrons and are oxidised.

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26
Q

Why are carbon electrodes chosen?

A

Carbon electrodes are chosen because they have a high melting point and they do not react with the reactants and the products (they are inert).

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27
Q

What is the general equation for the reaction between metal carbonate and an acid?

A

Metal carbonate + acid -> salt + water + co2

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28
Q

What is the general equation for the reaction between metal oxides/hydroxides and an acid?

A

metal oxide/hydroxide + acid -> a salt + water

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29
Q

What do acids and alkalis produce in an aqueous solution?

A

Acids produce hydrogen ions. Alkalis produce hydroxide ions.

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30
Q

State the general equation for a neutralisation reaction in short ionic form.

A

H+ + OH- -> H20

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31
Q

How is aluminium manufactured and why is it expensive?

A

It is made through the electrolysis of cryolite and aluminium oxide.
It is expensive because lots of energy is needed to produce the current.

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32
Q

Why is cryolite used in the extraction of aluminium?

A

Because it lowers the melting point of aluminium oxide. Reducing energy costs.

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33
Q

What are the half equations in the extraction of aluminium?

A

Al(3+) + 3e- -> Al (cathode)
2O(2-) -> O2 + 4e- (anode)
Oxygen reacts with carbon at the anode forming C02

34
Q

What is a redox reaction?

A

A reduction or oxidation reaction.

35
Q

What is an ionic equation?

A

Where you only show the particles that are oxidized or reduced. e.g. Ca + Fe(2+) –> Ca(+) + Fe

36
Q

What are ionic half equations?

A

Focuses on the ionic change of one particular element. e.g. Fe(2+) + 2e(-) –> Fe

37
Q

What are the products when calcium hydroxide and hydrochloric acid react?

A

Calcium chloride + water

38
Q

What is used to measure the unknown volume in a titration?

A

Burette

39
Q

Why are trains powered by hydrogen fuel cells being referred to as the new steam trains?

A

In hydrogen fuel cells hydrogen goes to the positive electrode where it loses electrons and is, therefore, oxidized. This means it produces water.

40
Q

Why must the positive electrode be continually replaced during the production of aluminium?

A

The carbon electrode reacts with the oxygen formed at the anode, which produces carbon dioxide. Meaning the electrode will corrode.

41
Q

Why can’t sodium chloride solution be used as the electrolyte to produce sodium metal?

A

The less reactive metal will from at the positive electrode.
Meaning hydrogen will form instead of sodium.

42
Q

Why do alkaline batteries eventually stop working?

A

A reactant is being used up

43
Q

Why can alkaline batteries not be recharged?

A

The reaction is not reversible.

44
Q

What is a cell?

A

A cell is composed of two electrodes dipped in an electrolyte solution. It creates a current from a chemical reaction.

45
Q

How are metals less reactive than carbon extracted.

A

Reduction with carbon. Carbon displaces the metal in a metal oxide. Leaving the metal in it’s pure form.

46
Q

What is the general equation for a reaction between metals and acids?

A

Metal + acid -> salt + hydrogen

47
Q

Which metals in the reactivity series will react with an acid?

A

Those above hydrogen.

48
Q

State a neutralisation reaction in ionic form.

A

H+ + OH- -> H2O

49
Q

Where does reduction occur in electrolysis?

A

Cathode

50
Q

Where does oxidation occur in electrolysis?

A

Anode

51
Q

How is aluminium manufactured?

A

Electrolysis of aluminium oxide and cryolite.

52
Q

Why is manufacturing aluminium expensive?

A

Lots of energy needed to produce the current.

53
Q

What is the difference between a chemical cell and electrolysis?

A

Electrolysis uses electricity to produce a chemical reaction.
A chemical cell uses a chemical reaction to produce electricity.

54
Q

Why is graphite used as an electrode?

A

Conducts electricity.
Inert (unreactive)

55
Q

Why does the metal in electrolysis need to be more reactive than carbon?

A

So it doesn’t get displaced by carbon.

56
Q

What is an alkali?

A

A base that dissolves in water to form a solution with a pH greater than 7.

57
Q

What is a base?

A

Any substance with a pH greater than 7.

58
Q

What are 3 common acids?

A

Nitric
Sulfuric
Hydrochloric

59
Q

What are 3 common bases?

A

Metal Carbonate
Metal Hydroxide
Metal oxide

60
Q

How should we evaporate the water in crystallisation and why?

A

Water bath/ electric heater
To avoid damaging the salt

61
Q

Why is a pipette and a burette used in a titration?

A

Pipette used to measure fixed volume.
Burette used to measure variable volume.

62
Q

Give 4 factors that affect the voltage produced by a cell.

A

Type of electrode.
Type of electrolyte.
Concentration of electrolyte
Temperature.

63
Q

What is a cell?

A

A cell is composed of two electrodes dipped in an electrolyte solution. It produces current from a chemical reaction.

64
Q

What is a battery?

A

Two or more cells connected in series.

65
Q

Explain rechargeable batteries.

A

Chemical reactions are reversed when external current is supplied.

66
Q

Explain non-rechargeable batteries.

A

All reactants are used up, cannot be recharged.

67
Q

What is a fuel cell?

A

Fuel cells consist of fuel and oxygen. Where the fuel is oxidised to produce electricity.

68
Q

What is a hydrogen fuel cell?

A

Where hydrogen is oxidised to form water.

69
Q

Why should batteries not be put in household waste?

A

Alkaline waste can be harmful / toxic / corrosive.

70
Q

What are the adv. of alkaline cells?

A

Cheap to manufacture.

71
Q

What are the disadv. of alkaline cells?

A

Expensive to recycle.
Toxic waste.
May end up in landfill sites.

72
Q

What is the overall equation for a hydrogen fuel cell?

A

Hydrogen + oxygen -> water

73
Q

What is the difference between hydrogen fuel cells and electrolysis?

A

Electrolysis - anode is positive and cathode is negative
Hydrogen fuel cells - cathode is positive and anode is negative

74
Q

What is the anode in both electrolysis and hydrogen fuel cells?

A

Where electrons are lost.

75
Q

Difference between an alkali and a base.

A

Alkali is an soluble metal hydroxide, a base is a insoluble metal hydroxide or metal oxide.

76
Q

What are all the charges of ions from acids?

A

Hydrochloric acid - Cl-
Nitric acid - NO3-
Sulfuric acid - SO42-

77
Q

What happens when the concentration of H+ ions increases by a factor of 10?

A

pH decreases by 1 unit.

78
Q

What forms from a metal + acid?

A

Salt + hydrogen

79
Q

How can soluble salts be made?

A

By reacting acids with insoluble solids such as metal, metal oxide, metal hydroxide and metal carbonate.

80
Q

How are metal oxides made?

A

Metal + oxygen

Chemistry (10 decks)

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