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지시엣이 Chemistry > C4 - Chemical Changes > Flashcards

C4 - Chemical Changes Flashcards

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1
Q

pH scale

A

A measure of how acidic or alkaline a solution is

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2
Q

lower pH means

A

The more acidic it is

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3
Q

higher pH means

A

More alkaline it is

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4
Q

pH7 is a …

A

neutral substance

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5
Q

pH indicator

A

A dye that changes colour depending on whether it’s above or below a certain pH. Some indicators contain a mixture of dyes that means they gradually change colour over a broad range of pH. These are called wide range indicators and they’re ysefyl for estimating the pH of a solution.

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6
Q

Universal Indicator

A

Standard ph indicator

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7
Q

pH meter

A

Consists of a pH probe used to measure pH electronically. It displays a numerical value which is more accurate than an indicator

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8
Q

What do acids form?

A

Aqueous solutions with a pH of less than 7.

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9
Q

What do acids form in water?

A

H+ ions

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10
Q

Base

A

A substance with a pH greater than 7

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11
Q

Alkali

A
  • Base that dissolves in water to form a solution

- pH greater than 7

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12
Q

What do Alkalis form in water?

A

OH- ions

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13
Q

Neutralisation

A

The reaction between acids and bases

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14
Q

Neutralisation word equation

A

acid + base -> salt + water

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15
Q

Neutralisation equation with terns if H+ and OH- ions

A

H+(aq) + OH-(aq) -> H2O(l)

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16
Q

What happens to the products of neutralisation?

A
  • Products are neutral (have a pH of 7)

- An indicator can be used to show that a neutralisation reaction is over

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17
Q

What do acids produce in water?

A

They produce hydrogen ions, H+

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18
Q

Strong acids

A

Ionise completely in water. All acid particles dissociate to release H+ ions

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19
Q

Weak acids

A

Don’t fully ionise in solution. Only a small proportion of acid particles dissociate to release H+ ions

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20
Q

Ionisation of a weak acid

A
  • Reversible reaction
  • Sets up an equilibrium between the undissociated and dissociated acid
  • Since only a few of the acid particles release H+ ions, the position of equilibrium lies well to the left
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21
Q

How does the concentration of H+ ions in the solution change the reaction?

A

If the concentration of H+ ions is higher, the rate of concentration will be faster, so strong acids will be more reactive than weak acids of the same concentration.

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22
Q

What does pH determine in an acid or alkali?

A

The measure of concentration of H+ ions in the solution

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23
Q

For every decrease of 1 on the pH scale, what happens to the concentration of H+ ions?

A

Increases by a factor of 10

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24
Q

pH of strong acid vs weak acid in the same concentration

A

pH of a strong acid is always less than pH of a weak acid

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25
Q

Acid strength

A

Proportion of the acid molecules ionise in water

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26
Q

What does concentration measure in acids

A

How much acid there is in a certain volume of water

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27
Q

Relation between pH and concentration

A

pH decreases when acid concentration increases

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28
Q

Are metal oxides and metal hydroxides alkalis?

A

Yes

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29
Q

What happens when bases don’t dissolve in water?

A

It doesn’t matter because neutralisation still takes place

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30
Q

How do metal carbonates change the the products of neutralisation?

A

Products are now salt, water and carbon dioxide

31
Q

Reactivity series

A
  • Potassium
  • Sodium
  • Lithium
  • Calcium
  • Magnesium
  • Carbon
  • Zinc
  • Iron
  • Hydrogen
  • Copper
32
Q

How are metals listed in the Reactivity Series?

A
  • How reactive they are towards other substances
  • The higher up it is, the more easily the form positive ions
  • A higher metal reacts easily with water or an acid
33
Q

How can a reaction between metals and acids reflect their reactivity?

A
  • The faster the reaction is (when there are more hydrogen bubbles being given off), the more reactive the metal is
34
Q

Oxidation

A

The reaction with oxygen to form oxides

35
Q

Reduction reaction

A

A reaction that separates a metal from its oxide

36
Q

Oxidation is gain of …

A

Oxygen to make an oxide

37
Q

Reduction is loss of …

A

Oxygen to make the pure metal

38
Q

What are some other ways to extract metals?

A
  • With carbon using reduction
  • The ore is reduced as oxygen is removed, and the carbon is oxidised with oxygen
  • The position of the metal in the reactivity series determines whether it can be extracted with carbon
39
Q

If the position of a metal is higher than carbon, we can extract the metal using …

A

Electrolysis

40
Q

If the position of a metal is lower than carbon, we can extract the metal using …

A

Reduction using carbon

41
Q

Why can some metals be mined in it’s elemental form?

A

They are so unreactive

42
Q

Oxidation (electrons)

A

The loss of electrons

43
Q

Reduction (electrons)

A

A gain of electrons

44
Q

OIL RIG (electrons)

A

Oxidation Is Loss, Reduction Is Gain

45
Q

REDOX

A

REDuction and OXidation happen at the same time

46
Q

Displacement reactions

A

A metal kicking another one out of a compound

47
Q

Rule for displacement reactions

A

A more reactive metal will displace a less reactive metal from its compound

48
Q

What is reduced in displacement reactions?

A

The metal ion

49
Q

What is oxidised in displacement reactions?

A

The metal atom

50
Q

Ionic equation

A

The particles that react and the products they form are shown (focuses on the substances which are oxidised or reduced)

51
Q

Spectator ions

A

Ions that don’t change in the reaction, which you can just not write in the equation

52
Q

Electrolysis

A

The chemical decomposition produced by passing an electric current through a liquid or solution containing ions.

53
Q

Where do the positive ions in the electrolyte move to?

A
  • Cathode (-ve electrode)

- Reduction (gain electrons)

54
Q

Where do the negative ions in the electrolyte move?

A
  • Move towards the anode (+ve electrode)

- Oxidised (lose electrons)

55
Q

Why is a flow of charge created through the electrolyte?

A

Ions travel to the electrodes

56
Q

What happens when ions gain or lose electrons during electrolysis?

A

They form the uncharged element and are discharged from the electrolyte

57
Q

Electrolyte

A

The liquid or solution that can conduct electricity

58
Q

Electrode

A

A solid that conducts electricity and is submerged in the electrolyte

59
Q

Why can’t an ionic solid be electrolysed?

A

The ions are in a fixed position and can’t move

60
Q

Why can molten ionic compounds be electrolysed?

A

The ions can move freely and conduct electricity

61
Q

What happens to molten liquids in electrolysis?

A

They are always broken up into their elements

62
Q

What happens to a positive metal ion during electrolysis?

A

They are reduced to the element at the cathode

63
Q

What happens to the non-metal ions during electrolysis?

A

They are oxidised to the element at the anode

64
Q

How to use electrolysis to extract aluminium from bauxite

A

1) Bauxite contains aluminium oxide Al2O3
2) Aluminium oxide has a very high melting temperature so it’s mixed with cryolite to lower the melting point
3) The molten mixture contains free ions - so it’ll conduct electricity
4) The positive Al^3+ ions are attracted to the negative electrode where they pick up 3 electrons and turn into neutral aluminium atoms. They sink to the bottom of the electrolysis tank
5) Negative O2- ions are attracted to the positive electrode where they each lose 2 electrons. The neutral oxygen atoms will then combine to form O2 molecules

65
Q

What else do you have to factor when you electrolyse an aqueous solutions?

A
  • The ions in the water
  • Hydrogen ions (H+)
  • Hydroxide ions (OH-)
66
Q

Ionic equation for water

A

H2O(l) H+(aq) + OH-(aq)

67
Q

What happens when a metal ions form an element that is more reactive than hydrogen during the process of electrolysis at the code in an aqueous solution?

A

If h+ ions and metal ions are present, hydrogen gas will ve produced

68
Q

At the anode, if OH- and halide ions are present, what forms?

A
  • The halogens will be formed
69
Q

What happens at the cathode during electrolysis in an aqueous solution if the metal ions form an element that is less reactive than hydrogen?

A

A solid layer of the pure metal will be produced instead

70
Q

What happens at the anode if no halide ions are present?

A

The OH- ions are discharged an oxygen will be formed

71
Q

How to test for chlorine?

A

Damps litmus paper turning it white

72
Q

How to test for hydrogen?

A

Makes a “squeaky pop” with a lighted splint

73
Q

How to test for oxygen?

A

Relight a glowing splint

74
Q

What do half equations show?

A

The reactions at the electrodes (make sure that the number of electrons need to be the same for each half equation)

지시엣이 Chemistry (10 decks)

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