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GCSE Chemistry > C3.3/4 - Acids/Electrolysis > Flashcards

C3.3/4 - Acids/Electrolysis Flashcards

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1
Q

Metals and acid always make…

A

Salt and hydrogen (MASH)

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2
Q

Metal oxides (bases) and acid always makes

A

Water and salt (BAWS)

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3
Q

Metal hydroxides (alkalis) and acid always makes

A

Water and salt (AAWS)

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4
Q

Metal carbonates and acid always makes

A

Water and carbon dioxide and salts (CAWCS)

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5
Q

How do you know if acids are strong or weak?

A

It depends on how well they ionise one water

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6
Q

What are some examples of strong acids

A 
Hydrochloride acid (HCL) 
Sulphuric acid (H2SO4)
Nitric acid (HNO3)
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7
Q

What are some examples of a weak acid

A

Acetic acid (CH3COOH)

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8
Q

Which acids ionise or dissociate completely in water

A

Strong acids

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9
Q

Which acids have only a few of acid molecules that ionise

A

Weak

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10
Q

What are chemicals made up of and what are they

A

Chemicals are substances

They are also made up of elements, compounds and mixtures

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11
Q

What are elements

A

Pure substances containing one type of atom

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12
Q

What are compounds

A

Chemically joined elements e.g. alloy is more than 2 metas joined

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13
Q

Mixtures can be what?

A

Can be separated e.g. evaporation

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14
Q

What are 3 examples of compounds

A

•acids ( all contain hydrogen and make H+)

  • alloy
  • covalent molecules
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15
Q

What are neutralisation reactions

A

When an acid reacts with an alkali or base to form a salt plus water

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16
Q

What can aqueous neutralisations be generalised as

A

H+ (aq) + OH- (aq) —> H2O (l)

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17
Q

What happens to the ph value of a solution when hydrogen ion concentration increases by a factor of ten

A

The pH value of a solution decreases by a factor of one

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18
Q

What are bases

A

Bases are substances that react with acids to neutralise them

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19
Q

What are 2 examples of bases

A
  • metal oxides e.g. caO (solid)

* metal hydroxides e.g. Ca (OH) 2 (aqueous)

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20
Q

If some metals e.g. Ca only react with acids, is this a base

A

NO

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21
Q

What are alkalis

A

Alkalis are substances that dissolve (and ionise) in water to form hydroxide ions. An alkali is a double base

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22
Q

What are 2 examples of alkalis

A
  • NaOH —> Na+ + OH-

* ca (OH) 2 —> Ca 2+ + 2OH-

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23
Q

NH3 is an alkali because…

A

It forms OH- ions when added to water

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24
Q

What is the word equation for the thermite reaction

A

Iron oxide + aluminium -> aluminium oxide + iron

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25
Q

What is a redox reaction

A

When electrons are exchanged in the thermite reaction

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26
Q

What do redox reactions involve

A

Redox reactions involve the transfer of electrons

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27
Q

What is a titration

A

A titration is a reaction in which we measure exactly what volume of two solutions will react together e.g. measuring the volume of acid needed to neutralise a measured volume of alkali

28
Q

What is the endpoint of a reaction

A

The endpoint is the point where a reaction finishes - for acid-base titrations this is where the pH reaches neutral

29
Q

What is concentration always measured in

A

Mol/dm3

30
Q

1 dm 3 = ? = ?

A

1dm3 = 1000cm3 = 1000ml

31
Q

MOLE EQUATION

How do I work out moles?

A

Concentration X volume

32
Q

MOLE EQUATION

How do I work out the concentration?

A

Moles divided by volume

33
Q

MOLE EQUATION

How do I work out volume?

A

Moles divided by concentration

34
Q

What is the equation for the full dissociation of HCI

A

HCI -> H+ + Cl -

35
Q

What is the equation for the partial dissociation for CH3COOH

A

CH3COOH —> CH3COOH- + H+

36
Q

What is the ionic equation for neutralisation

A

H+ (aq) + OH- (aq) —> H2O (L)

37
Q

What is acid strength

A

Acid strength (strong / weak) tells you what proportion of the acid molecules ionise in water

38
Q

What does acid concentration measure

A

Concentration measures how much acid there is in a litre (1dm3) if water. Concentration is basically how watered down your acid is

39
Q

How can acid concentration and strength affect pH

A

Because both affect the concentration of H+ ions e.g. W strong acid can be diluted to obtain a pH like that of a weak acid

40
Q

What is a pH curve

A

A graph of pH (vertical axis) against total volume of acid or alkali added (on horizontal axis)

41
Q

What do titration curves show and what are they used to show

A

Titration curves show pH changes with volume and titration curves are used to show where neutralisation happens during a titration

42
Q

What happens at the vertical point in a titration or pH curve

A

The solution is neutral (at pH 7). This is called the end point of the titration

43
Q

What is stage 1 of copper being purified by electrolysis

A

The positive electrode is impure copper ; the negative electrode is pure copper : the electrolyte is copper sulfate solution

44
Q

What is stage 2 of copper being purified by electrolysis

A

The positive electrode gets smaller as it dissolves ; the negative electrode gets bigger as it’s coated with copper

45
Q

What is stage 3 of copper being purified by electrolysis

A

Copper ions (cu2+) in the electrolyte are attracted to the negative electrode. Each cu2+ gains two electrons to form a copper stool, which sticks to the electrode. This is reduction

46
Q

What is stage 4 of copper being purified by electrolysis

A

Copper atoms in the positive electrode can lose two electrons to form copper ions (cu2+) which dissolve into the electrolyte. This is oxidation

47
Q

What is stage 5 of copper being purified by electrolysis

A

As the copper ions (cu2+) are released at the positive electrode, atoms of impurities in the impure copper also become free. The mud they form is collected as it may contain silver and gold

48
Q

What is oxidation

A

If electrons are lost (Mg2+)

49
Q

What is reduction

A

If the electrons are gained (2Cl-)

50
Q

What is electrolysis

A

The process by which ionic substances are broken down into simpler substances by passing an electric current through them

51
Q

What is an electrolyte

A

A liquid in which a current can pass through (e.g. a molten ionic substance or an aqueous ionic solution). This is the liquid that the electrodes are placed in

52
Q

What is an electrode

A

A conductor (e.g. metal) which allows electricity (electrons) to pass through. This is the solid substance placed into the electrolyte. Commonly made from graphite is high is inert

53
Q

Electrons move towards the…

A

Negative cathode. Here positive ions can gain the electrons they need - reduction occurs

54
Q

Electrons are lost from negative ions during oxidation at the…

A

Positive anode and the electrons flow form the positive anode to the negative cathode

55
Q

In your electrolyte you have cations. What are cations?

A

Positively charged ions

56
Q

In your electrolyte you have anions. What are anions?

A

Negatively charged ions

57
Q

Opposite charges attract, so what will the anions be attracted to?

A

The anions will be attracted to the anode (positive electrode) these ions will LOSE electrons - oxidation occurs

58
Q

Opposite charges attract so what will the cations be attracted to?

A

The cations will be attracted to the cathode (negative electrode). These ions will gain electrons - reduction occurs

59
Q

What do you need for electrolysis to occur

A

A power source for example a battery

60
Q

What do +anode attract

A

Attracts -ions (anions)

61
Q

What do -cathode attract

A

Attracts +ions (cations)

62
Q

What happens if -ions are halogens I.e.

Chloride CL-
Bromide Br-
Iodine I-

A

The halogen is produced

63
Q

If +ions (metals) are more reactive than hydrogen for example

K,Na, Ca,Mg,Zn,Fe

What happens?

A

Hydrogen is produced

64
Q

If -ions are not halogens e.g.

Sulphate SO42-
Nitrate NO3-
Carbonate CO32-

What happens

A

Oxygen is produced from the OH-

65
Q

If +ions (metals) are less reactive than hydrogen for example

Cu, Ag, Au

What happens?

A

Then the metal is produced

GCSE Chemistry (12 decks)

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