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Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

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1
Q

Range of pH scale

A

0 to 14

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2
Q

What is lower on pH scale

A

More acidic solutions

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3
Q

What is higher on pH scale

A

More alkaline solutions

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4
Q

pH of neutral substances

A

7

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5
Q

What do you use to measure pH of a solution

A

An indicator

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6
Q

Indicator

A

Dye that changes colour depending on whether it’s above or below a certain pH

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7
Q

Wide range indicator

A

Indicator that contains a mixture of dyes so they gradually change colour over a broad range of pH

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8
Q

Example of wide range indicator

A

Universal indicator

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9
Q

Colour of acidic solutions on universal indicator

A

Orange-red

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10
Q

Colour of alkaline solution on universal indicator

A

Blue-purple

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11
Q

Colour of neutral solution on universal indicator

A

Green

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12
Q

How to measure pH electronically

A
  • pH probe and pH meter
  • probe placed in solution, meter gives numerical value of pH
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13
Q

More accurate method of measuring pH

A

pH probe and pH indicator

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14
Q

Acid

A

Substance that forms aqueous solutions with pH less than 7

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15
Q

What ions do acids form in water

A

H⁺

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16
Q

Base

A

A substance with pH greater than 7

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17
Q

Alkali

A

Base that dissolves in water to form a solution with pH greater than 7

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18
Q

What ions do alkalis form in water

A

OH⁻

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19
Q

Neutralisation

A

Reaction between acid and base

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20
Q

Neutralisation reaction word equation

A

acid + base —> salt + water

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21
Q

Neutralisation reaction between acids and alkalis symbol equation

A

H⁺ + OH⁻ —> H₂O

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22
Q

What happens when an acid/alkali neutralise each other

A

Products will be neutral with pH 7

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23
Q

What happens to strong acids in water

A
  • ionise completely
  • all acid particles dissociate to release H⁺ ions
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24
Q

What happens to weak acids in water

A
  • do not fully ionise
  • small proportion of acid particles dissociate to release H⁺ ions
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25
Q

Is ionisation of weak acids reversible

A

Yes

26
Q

Why is ionisation of weak acids reversible

A
  • reaction sets up equilibrium between undissociated and dissociated acid
    as only a few acids particles release H⁺, equalibrium position lies well to left
27
Q

Which kind of acid is more reactive

A

Stronger ones

28
Q

Why are stronger acids more reactive

A

Higher concentration of H⁺ ions increases reactivity

29
Q

pH

A

Measure of concentration of hydrogen (H⁺) ions in a solution

30
Q

What happens to concentration of H⁺ ions as pH decreases by 1

A

It increases by a factor of 10

31
Q

Formula for factor of change in H⁺ ion concentration

A

Factor H⁺ ion concentration changes by = 10⁻ˣ
X = change in pH

32
Q

Acid strength

A

Proportion of acid molecules that ionise in water

33
Q

Acid concentration

A

How much acid there is in a certain volume of water

34
Q

How does acid concentration affect pH

A

pH decreases as acid concentration increases

35
Q

Metal bases

A
  • metal oxide
  • metal hydroxide
  • metal carbonate
36
Q

Do metal oxides dissolve in water

A

Yes

37
Q

Do metal hydroxides dissolve in water

A

Yes

38
Q

Acid + metal oxide —>

A

Salt + water

39
Q

Acid + metal hydroxide —>

A

Salt + water

40
Q

Acid + metal carbonate —>

A

Salt + water + carbon dioxide

41
Q

Making salts practical

A
  • pick right acid and insoluble base
  • gently warm dilute acid with Bunsen burner, turn off
  • add insoluble base to acid a bit at a time until no more reacts - base is in excess and sinks to bottom of flask after stirring as all acid has been neutralised
  • filter out excess solid to get salt solution
  • pure/solid salt crystals - gently heat solution in water bath to evaporate some water, stop, leave solution to cool, crystals form to be filtered + dried
42
Q

What is reactivity series

A

List of metals in order of reactivity towards other substances

43
Q

Reactivity series

A
  • potassium
  • sodium
  • calcium
  • magnesium
  • aluminium
  • carbon
  • zinc
  • iron
  • lead
  • tin
  • hydrogen
  • copper
  • silver
  • gold
  • platinum
44
Q

What determines reactivity of metals

A

How easily they lose electrons - forming positive ions

45
Q

What happens when metals react with water or acid

A

Lose electrons - forming positive ions

46
Q

Acid + metal —>

A

Salt + hydrogen

47
Q

What indicates speed of reaction between acid and metal

A

Rate at which bubbles of hydrogen are given off

48
Q

How to more reactive metals react

A
  • faster
  • explosively
49
Q

How do less reactive metals react

A
  • slower
  • less violently
50
Q

Metal + water —>

A

Metal hydroxide + hydrogen

51
Q

Which metals will react with water

A

More reactive ones

52
Q

Oxidation in terms of oxygen

A
  • metals reacting with oxygen to form oxides
  • gain of oxygen
53
Q

Reduction in terms of oxygen

A
  • reaction that separates a metal from it’s oxide
  • loss of oxygen
54
Q

How can some metals be extracted by reduction with carbon

A
  • metal reacted with carbon
  • ore is reduced as oxygen is removed from it
  • carbon gains oxygen and is oxidised
55
Q

Which metals are extracted by electrolysis

A

Metals above carbon on reactivity series

56
Q

Which metals are extracted by reduction using carbon

A

Metals below carbon on reactivity series

57
Q

Why are some elements mined in elemental form

A

They are so unreactive

58
Q

Oxidation in terms of electrons

A

Loss of electrons

59
Q

Reduction in terms of electrons

A

Gain of electrons

60
Q

Redox reaction

A

Reaction where reduction and oxidation happen at the same time

61
Q

Displacement reaction

A

Redox reaction where a more reactive metal displaces a less reactive metal from its compound

62
Q
A

Chemistry (6 decks)

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