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GCSE Chemistry OCR A > C3 > Flashcards

C3 Flashcards

1
Q

What elements are diatomic?

A

All of group 7
Oxygen
Hydrogen
Nitrogen

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2
Q

What does Sulfur molecules exist as?

A

S8

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3
Q

What is the molecule phosphorus ?

A

P4

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4
Q

What does the molecular formula show?

A

The symbol for each element and the number of atoms in each element

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5
Q

Hydroxide ion:

A

OH-

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6
Q

Nitrate ion

A

NO3-

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7
Q

Carbonate ion:

A

CO3 2-

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8
Q

Sulfate ion

A

SO4 2-

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9
Q

How do you form ionic compounds?

A

Switch their charge number for a subscript number but the other way round

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10
Q

Ammonium ion

A

NH4 +

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11
Q

What is the law of conservation of mass?

A

During a chemical reaction no atoms are created or destroyed

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12
Q

What is the explanation if the mass increased?

A

One of reactants was a gas (which wasn’t weighed)

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13
Q

What is the explanation for when mass decreases

A

One of the products was a gas escaped and therefore mass was not accounted for

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14
Q

How do you show that mass has been conserved in a reaction?

A

Add up the relative masses (Mr) of each side to see that they are the same

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15
Q

Ammonia

A

NH3

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16
Q

What does aqueous mean?

A

Dissolved in water

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17
Q

How do you balance equations?

A

Use big numbers
Make sure there are the same amount of atoms on one side than the other
Do hydrogen and oxygen last

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18
Q

How do you write half equations?

A

Focus on one reactant, whether it lost of gained electrons
*one side will be neutral and the other will have a charge
If lost electrons instead of subtracting m add in the other side

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19
Q

Half equations rules

A

If became positive: lost electrons
If became negative: gained electrons

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20
Q

How do you write ionic equations

A

Exclude the spectator ions
Write the charge and state for the remainder

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21
Q

What are spectator ions?

A

Ions that do not change state or charge in a reaction

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22
Q

What state is a precipitate?

A

Solid

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23
Q

What is the definition of a mole?

A

amount of substance that contains the same number of particles (6.02 × 1023) as there are atoms in 12.0 g of 12C

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24
Q

What is the definition for avogadro’s constant?

A

The number of entities in one mole , equal to the number of atoms in 12g of carbon-12 atoms

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25
Q

What is the value of avogradro’s constant?

A

6.02 ✖️10^ 23

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26
Q

How many molecules and atoms are in one mol of water?

A

6.02✖️10^23 molecules
(6.02✖️10^23) ✖️3 atoms

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27
Q

How do you calculate the mass of a mole of a substance?

A

You find the Mr (relative formula mass) for that substance

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28
Q

How do you find the mean mass of one atom?

A

Mean mass of one atom = Mr➗ Avogadro’s constant

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29
Q

What equation do you use for reacting masses?

A

Mass = moles✖️Mr

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30
Q

How do you calculate reacting masses?

A
  1. Circle the two part involved
  2. Find the mols
    IGNORE ANY BIG NUMBERS
  3. Find the ratio
  4. Convert it back to mass
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31
Q

How do you balance the equation with stoichiometry?

A
  1. From the masses find the moles for each element
  2. Put it in the simplest ratio
  3. These become the big number
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32
Q

What is the limiting reactant ?

A

The reactant in least amount deciding the amount of product

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33
Q

What must you always remember to do?

A

Round to 3.s.f

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34
Q

How do you find out the limiting reactant?

A
  1. Find the amount of moles in each one
  2. Find the original ratio and the ratio the other two give
  3. Whichever one does not for the old ratio ,eg
    lower is limiting and higher is excess
35
Q

Why is a reaction endothermic?

A

Bond breaking is endothermic
Bond making is exothermic
There was more bond breaking than making.
More energy taken in than released

36
Q

Endothermic?

A

Taking energy in
Making surroundings cooler
Eg: photosynthesis

37
Q

Why is a reaction exothermic

A

Bond breaking is endothermic
Bond making is exothermic
More bond making than breaking
More energy given out then taken in

38
Q

Exothermic?

A

Giving energy out to surroundings
Hot
Eg: combustion/neutralisation

39
Q

What is activation energy?

A

The minimum amount on of energy required to start a reaction

40
Q

What should an endothermic reaction profile look like?

A

📈products higher than reactants
Takes in energy for itself
📈 y axis = energy
📈 x axis = progress of reaction
📈 activation energy line from reactants to peak
📈 positive energy change from reactants to products

41
Q

What should an exothermic reaction profile look like?

A

📉reactants higher than products
Gives our energy
📉y axis = energy
📉x axis = profess of reaction
📉activation energy from reactants to peak
📉negative energy change

42
Q

What is energy change

A

Difference between energy transferred FROM surroundings to break bonds and between energy transferred TO the surroundings when bond making

43
Q

What is bond energy?

A

The energy needed to break 1 mol of a particular covalent bond
Units = KJ/mol

44
Q

What are redox reactions?

A

Reduction = loss of oxygen
Gain of electrons
Oxidation =gain of oxygen
Loss of electrons
OILRIG

45
Q

How do you find oxidising and reducing agents?

A

Oxidising agent is the thing that got reduced
Reducing agent is the thing that got oxidised
* both can only be reactants

46
Q

What is hydrochloric acid

47
Q

Sulphuric acid

48
Q

Nitric acid

49
Q

What is a metal(s) + acid

A

Salt + hydrogen

50
Q

What is a metal oxide(s) + acid

A

Salt+ water

51
Q

What is metal hydroxide +acid an state of metal hydroxide?

A

Salt+water
Metal hydroxide =aq

52
Q

What is metal carbonate(s) +acid

A

Salt+water+carbon dioxide

53
Q

What do acid’s release?

54
Q

What do alkali’s release?

55
Q

What is the difference between an alkaline and a base

A

Alkali’s are bases that are soluable

56
Q

Describe the pH scale

A

Neutral = 7
Acid =<7
Alkali = > 7

57
Q

How do you measure pH?

A

Use a pH meter:
1. Wash the probe
2. Put it in calibration buffer and adjust the reading
3. Put in in solution
Wash between each reading to prevent contamination

58
Q

What is neutralisation?

A

A reaction an acid and a base to form a salt and water

59
Q

What is the neutralisation equation?

A

H+ ➕OH- = H2O
aq ➕aq = l

60
Q

What would you see when a metal carbonate/ metal is reacting?

A

Fizzing /effervescent
Because carbon dioxide / hydrogen is being released

61
Q

What is the difference between dilute and concentrated acids?

A

Concentrated mean a high ratio of
Amount of Acid : volume of solution

62
Q

Why are acids diluted?

A

To make them more safe

63
Q

What is the difference between weak and strong acids ?

A

Weak acids only partially ionise (release H+ ions)
Strong acids fully ionise (release H+ ions)
*in aq solutions
Strong acids all so have a lower pH

64
Q

What is the sign for a reaction that does not go to completion?

A

Half way arrows
Weak acid - partially ionising

65
Q

What is the link between concentration and pH

A

As the concentrated ions increase by a factor of 10, the pH decreases by 1

66
Q

What do titrations show?

A

How much of an acid is used to neutralise a bas

67
Q

How do you read a titration curve?

A

X axis= volume of base/acid added
Y axis = pH
Vertices line = how much makes it neutral

68
Q

What is electrolysis ?

A

The separation of compounds using electricity

69
Q

What is an electrolyte ?

A

The solution or compound the electrodes are placed in

70
Q

What is a cathode?

A

The negative electrode
Attracting positive ions

71
Q

What is the anode?

A

The positive electrode
Attracting negative ions

72
Q

What happens during molten electrolysis?

A

Positive ions gain electrons from the cathode to become neutral atoms (reduction)
Negative ions lose electrons at the anode to become neutral atoms (oxidation)

73
Q

What are inert electrodes?

A

Electrodes that do not react, used in molten and aqueous electrolysis .
Eg: copper/platinum

74
Q

What are the rules of aqueous electrolysis at the cathode?

A

If the metal is a known one (gold/silver/copper) - more un reactive then hydrogen then it will be discharged.
2H+ ➕2e- ➡️H2 a gas

75
Q

What are the rules of aqueous electrolysis at the anode ?

A

Unless a halide is present hydroxide will be discharged
4OH-➡️2H2O ➕02➕4e-

76
Q

What happens in aqueous electrolysis when there are complex molecules?

A

Say hydroxide gets discharged which is oxygen

77
Q

What is the reactivity series acronym?

A

Please stop calling me a zombie in class

78
Q

How does electroplating work ?

A

Cathode = thing you are trying to plate
Anode = thing you want to plate it with eg: silver
Electrolyte: must have the same metal as the anode
Cations(metal) moves from solution to anode, they are then replaced by the anode they loose electrons making them ions

79
Q

What happens at the electrodes in electroplating?

A

Anode : loosing electrons to become ions
Ag ➖e- ➡️Ag-
Cathode : gaining lectins to become neutral
Ag+ ➕e-➡️Ag

80
Q

How is copper purified?

A

Anode = impure copper
Cathode = pure copper
Electrolyte = copper sulphate
Copper ions from solution go to the cathode and ions made from the anode replace. Impurities/sludges is deposited at the bottom

81
Q

What happens at the electrodes in copper purification?

A

Anode: losing electrons
Cu ➖2e-➡️cu2+
Cathode: gaining electrons to become neural
Cu2+ ➕2e- ➡️cu

82
Q

Why can molten ionic solutions conduct?

A

The IONS are free to move and so can carry a charge

83
Q

What is the unit of Avogrodro constant?

84
Q

What is the unit of avagradro’s constant?

GCSE Chemistry OCR A (10 decks)

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