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Chemistry Paper 1 > Chemical Changes > Flashcards

Chemical Changes Flashcards

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1
Q

What are oxidation reactions?

A

Where metals react with oxygen to produce metal oxides, the substance gains oxygen.

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2
Q

What are reduction reactions?

A

Where a substance loses oxygen.

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3
Q

Oxidisation and reduction always…

A

Occur together

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4
Q

Properties of metal oxides

A
  • Metals react with oxygen to form metal oxides
  • Solids at room temperature
  • Are bases, if they dissolve they form alkaline solutions
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5
Q

Properties of non-metal oxides?

A
  • Usually gases at room temperature

- Dissolve in water to form acidic solutions

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6
Q

How can metal oxides be reduced?

A

By removing oxygen-
When lead (IV) oxide is heated with carbon:
The lead oxide loses oxygen so it is reduced
The carbon gains oxygen so it is oxidised

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7
Q

What is the reactivity of a metal related to?

A

Its tendency to form positive ions.

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8
Q

Which non-metals are often included in the reactivity series?

A

Hydrogen and carbon

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9
Q

A more reactive metal can…

A

Displace a less reactive metal from a compound.

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10
Q

What is an ore?

A

A material from which a metal or valuable mineral can be profitably extracted.

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11
Q

What are reaction of metals with water and acids limited to?

A

Room temperature and do not include reaction with steam.

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12
Q

What does the method of extracting a metal depend on?

A

How reactive it is

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13
Q

What do unreactive metals exist as?

A

Elements at the earth’s surface

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14
Q

What are most metals found as?

A

Metal oxides/compounds

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15
Q

How can metals less reactive than carbon be extracted from their oxides?

A

By heating with carbon

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16
Q

How do not all oxidation and reduction reactions involve oxygen?

A
  • Oxidation is loss of electrons

- Reduction is gain of electrons

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17
Q

What happens when substances dissolve in water?

A

They dissociate into their individual ions.

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18
Q

What do hydroxide ions (OH-) make solutions?

A

Alkaline

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19
Q

What do hydrogen ions (H+) make solutions?

A

Acidic

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20
Q

What is the PH scale?

A

A measure of the acidity or alkalinity of an aqueous solution:

  • A solution with a PH of 7 is neutral
  • less than 7= acidic
  • more than 7= alkaline
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21
Q

How can the PH of a solution be measured?

A

Using a PH probe or universal indicator.

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22
Q

What is a universal indicator?

A

A mixture of dies that show a range of colours to indicate how acidic or alkaline a substance is.

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23
Q

What are soluble bases?

A

Alkalis

24
Q

What are acids neutralised by?

A

Bases

25
Q

Acid + metal hydroxide ->

A

Salt + water

26
Q

What sort of ions do acids contain?

A

Hydrogen ions (H+)

27
Q

What sort of ions do alkalis contain?

A

Hydroxide ions OH-

28
Q

What happens when acids and alkalis react?

A

The hydrogen and hydroxide ions react to produce water with a PH of 7 meaning it is a neutralisation reaction.

29
Q

Metal oxide + acid ->

A

Salt + water

30
Q

Acid + metal carbonate ->

A

Salt + water + carbon dioxide

31
Q

When is a salt produced?

A

When the hydrogen in the acid is replaced by a metal ion

32
Q

The name of the salt produced depends on the acid used:

A
  • Hydrochloric acid produces chloride salts
  • Nitric acid produces nitrate salts
  • Sulphuric acid produces sulphate salts
33
Q

How can soluble salts be made?

A

By reacting acids with insoluble bases, such as metal oxides, metal hydroxides and metal carbonates.

34
Q

What happens to strong acids in water?

A

They are completely ionised

35
Q

What happens to weak acids in water?

A

They are only partially ionised.

36
Q

What is the PH of a solution?

A

A measure of the concentration of H+ ions

37
Q

What does a PH decrease of one unit indicate?

A

That the concentrations of hydrogen ions has increased by a factor of 10.

38
Q

What is electrolysis?

A

The use of an electrical current to break down compounds containing ions into their constituent elements.

39
Q

What is the substance being broken down by electrolysis called?

A

The electrolyte

40
Q

What are electrodes made from?

A

Solids that conducts electricity.

41
Q

During electrolysis:

A
  • Negatively charge ions move to the anode (the positive electrode)
  • Positively charge ions move to the cathode (the negative electrode)
42
Q

For electrolysis why much an ionic compound be either melted or dissolved in water?

A

So the ions are free to move around. Ions are discharges at the electrode to produce elements.

43
Q

What are positive ions called?

A

🐈

Cations

44
Q

What are negative ions?

A

Anions

45
Q

When does reduction occur in electrolysis?

A

When positively charge ions gain electrons at the cathode.

46
Q

When does oxidation occur in electrolysis?

A

When negatively charge ions gain electrons at the anode.

47
Q

What is a redox reaction?

A

Where both reduction and oxidation take place.

48
Q

How can metals more reactive than carbon he extracted from their ores?

A

Using electrolysis

49
Q

Why is electrolysis an expensive process?

A

It requires a lot of heat and electrical energy.

50
Q

How is aluminium obtained by electrolysis?

A

It is obtained by the electrolysis of aluminium oxide that has been mixed with cryolite (a compound of aluminium).

Aluminium forms at the cathode
Oxygen gas forms at anode which is made of carbon and reacts with the carbon forming carbon dioxide

51
Q

What does cryolite do?

A

Lowers the melting point of aluminium oxide, meaning less energy is needed.

52
Q

Why does the negative electrode have to be replaced regularly?

A

It is made of carbon and substances react with carbon meaning it gets worn away.

53
Q

When is it harder to predict the products of electrolysis?

A

When ionic compounds are dissolved in water.

54
Q

What do water molecules break down to from?

A

OH- and H+

55
Q

What is produced at the cathode if the metal ions are more and less reactive than hydrogen when an aqueous solution is electrolysed?

A

More: hydrogen
Less: a metal

56
Q

What is produced at the anode when aqueous solutions are electrolysed?

A

Oxygen is produced unless the solution contains Halide ions. If halide ions are present, the halogen is produced.

57
Q

In the electrolysis of sodium chloride solution:

A
  • Hydrogen released at cathode

- Chlorine has released at anode

Chemistry Paper 1 (5 decks)

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