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GCSE Chemistry OCR A > C3 > Flashcards

C3 Flashcards

(84 cards)

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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
What is the value of avogradro’s constant?
6.02 ✖️10^ 23
26
How many molecules and atoms are in one mol of water?
6.02✖️10^23 molecules (6.02✖️10^23) ✖️3 atoms
27
How do you calculate the mass of a mole of a substance?
You find the Mr (relative formula mass) for that substance
28
How do you find the mean mass of one atom?
Mean mass of one atom = Mr➗ Avogadro’s constant
29
What equation do you use for reacting masses?
Mass = moles✖️Mr
30
How do you calculate reacting masses?
1. Circle the two part involved 2. Find the mols IGNORE ANY BIG NUMBERS 3. Find the ratio 4. Convert it back to mass
31
How do you balance the equation with stoichiometry?
1. From the masses find the moles for each element 2. Put it in the simplest ratio 3. These become the big number
32
What is the limiting reactant ?
The reactant in least amount deciding the amount of product
33
What must you always remember to do?
Round to 3.s.f
34
How do you find out the limiting reactant?
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
Why is a reaction endothermic?
Bond breaking is endothermic Bond making is exothermic There was more bond breaking than making. More energy taken in than released
36
Endothermic?
Taking energy in Making surroundings cooler Eg: photosynthesis
37
Why is a reaction exothermic
Bond breaking is endothermic Bond making is exothermic More bond making than breaking More energy given out then taken in
38
Exothermic?
Giving energy out to surroundings Hot Eg: combustion/neutralisation
39
What is activation energy?
The minimum amount on of energy required to start a reaction
40
What should an endothermic reaction profile look like?
📈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
What should an exothermic reaction profile look like?
📉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
What is energy change
Difference between energy transferred FROM surroundings to break bonds and between energy transferred TO the surroundings when bond making
43
What is bond energy?
The energy needed to break 1 mol of a particular covalent bond Units = KJ/mol
44
What are redox reactions?
Reduction = loss of oxygen Gain of electrons Oxidation =gain of oxygen Loss of electrons OILRIG
45
How do you find oxidising and reducing agents?
Oxidising agent is the thing that got reduced Reducing agent is the thing that got oxidised * both can only be reactants
46
What is hydrochloric acid
HCl
47
Sulphuric acid
H2SO4
48
Nitric acid
NHO3
49
What is a metal(s) + acid
Salt + hydrogen
50
What is a metal oxide(s) + acid
Salt+ water
51
What is metal hydroxide +acid an state of metal hydroxide?
Salt+water Metal hydroxide =aq
52
What is metal carbonate(s) +acid
Salt+water+carbon dioxide
53
What do acid’s release?
H+ ions
54
What do alkali’s release?
OH-
55
What is the difference between an alkaline and a base
Alkali’s are bases that are soluable
56
Describe the pH scale
Neutral = 7 Acid =<7 Alkali = > 7
57
How do you measure pH?
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
What is neutralisation?
A reaction an acid and a base to form a salt and water
59
What is the neutralisation equation?
H+ ➕OH- = H2O aq ➕aq = l
60
What would you see when a metal carbonate/ metal is reacting?
Fizzing /effervescent Because carbon dioxide / hydrogen is being released
61
What is the difference between dilute and concentrated acids?
Concentrated mean a high ratio of Amount of Acid : volume of solution
62
Why are acids diluted?
To make them more safe
63
What is the difference between weak and strong acids ?
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
What is the sign for a reaction that does not go to completion?
Half way arrows Weak acid - partially ionising
65
What is the link between concentration and pH
As the concentrated ions increase by a factor of 10, the pH decreases by 1
66
What do titrations show?
How much of an acid is used to neutralise a bas
67
How do you read a titration curve?
X axis= volume of base/acid added Y axis = pH Vertices line = how much makes it neutral
68
What is electrolysis ?
The separation of compounds using electricity
69
What is an electrolyte ?
The solution or compound the electrodes are placed in
70
What is a cathode?
The negative electrode Attracting positive ions
71
What is the anode?
The positive electrode Attracting negative ions
72
What happens during molten electrolysis?
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
What are inert electrodes?
Electrodes that do not react, used in molten and aqueous electrolysis . Eg: copper/platinum
74
What are the rules of aqueous electrolysis at the cathode?
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
What are the rules of aqueous electrolysis at the anode ?
Unless a halide is present hydroxide will be discharged 4OH-➡️2H2O ➕02➕4e-
76
What happens in aqueous electrolysis when there are complex molecules?
Say hydroxide gets discharged which is oxygen
77
What is the reactivity series acronym?
Please stop calling me a zombie in class
78
How does electroplating work ?
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
What happens at the electrodes in electroplating?
Anode : loosing electrons to become ions Ag ➖e- ➡️Ag- Cathode : gaining lectins to become neutral Ag+ ➕e-➡️Ag
80
How is copper purified?
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
What happens at the electrodes in copper purification?
Anode: losing electrons Cu ➖2e-➡️cu2+ Cathode: gaining electrons to become neural Cu2+ ➕2e- ➡️cu
82
Why can molten ionic solutions conduct?
The IONS are free to move and so can carry a charge
83
What is the unit of Avogrodro constant?
1/mol
84
What is the unit of avagradro’s constant?
1/ mol

GCSE Chemistry OCR A (10 decks)

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