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Chemistry > C3 > Flashcards

C3 Flashcards

1
Q

What is a diatomic molecule?

A

Two atoms covalently bonded together, attracted to each other by weak intermolecular forces

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2
Q

What are examples of diatomic molecules?

A

Hydrogen
Nitrogen
Oxygen
Elements in group 7 (halogens)

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3
Q

What is the law of conservation of mass?

A

Atoms cannot be created or destroyed by chemical reactions. The same atoms are present at the start and end of a reaction

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4
Q

Why does mass change during some reactions?

A

Non-enclosed system - gases escape or leave the reactions

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5
Q

What is a half equation?

A

The model for the change that happens to 1 reactant in a chemical reaction

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6
Q

Where is the e- in a half equation when the atoms loses electrons?

A

After the arrow

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7
Q

Where is the e- in an equation where the atoms gains electrons?

A

Before the arrow

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8
Q

What is a complete ionic equation?

A

An equation that shows the ions present in a reaction mixture while including the formulae of any molecular substances present

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9
Q

What are spectator ions?

A

Ions that are in the reaction mixture but do not take part in the reaction

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10
Q

What does a net ionic equation do?

A

Leaves out the spectator ions

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11
Q

What is a precipitation reaction?

A

When an insoluble product (precipitate)is formed from 2 mixed solutions

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12
Q

What a mole?

A

The amount of any substance that contains the same number of entities as there are atoms in 12g of carbon 12

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13
Q

What is Avogadros’s constant?

A

6.02 x 10^23

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14
Q

How many enteritis are in 1 mol of a substance?

A

Avogadro’s constant - 6.02 x 10^23

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15
Q

What is the molar mass?

A

The mass of 1 mol of a substance (g/mol)

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16
Q

How do you work out molar mass?

A

Look at the Mr or Ar of a substance

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17
Q

What is the for Ila for masses of reactants and products?

A

Mass (g) = molar mass (g/mol) x amount (mol)

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18
Q

What is the limiting reactant?

A

The reactant that determines the amount of product formed (the reactant we have less of)

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19
Q

What is stoichiometry?

A

Balancing equations using moles

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20
Q

What happens during an exothermic reaction!

A

The temperature of the reaction mixture increases during a chemical reaction

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21
Q

What are examples of exothermic reactions?

A

Combustion
Neutralisation

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22
Q

What happens during an endothermic reaction?

A

The temperature of the reaction mixture decreases during a chemical reaction

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23
Q

What are examples of endothermic reactions?

A

Citric acid and sodium hydrogen carbonate - why they feel cold on the tongue
Photosynthesis

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24
Q

What is a reaction profile?

A

A chart that shows the energy involved

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25
How much energy is required in endothermic reactions?
The amount of energy transferred to break bonds is MORE than the energy transferred when new bonds form
26
What is the energy change in exothermic reactions?
Positive - overall, energy is transferred from the surroundings which cool down
27
What does an endothermic reaction look like on a reaction profile?
High activation energy with products having more energy than reactants
28
What is the overall transfer of energy in an exothermic reaction?
The amount of energy transferred to break bonds is LESS than the energy transferred when new bonds form
29
What is activation energy?
The minimum energy needed for a reaction to start
30
What is a redox reaction?
A reaction in which reduction and oxidation happen at the same time
31
What is reduction (in terms of oxygen)?
The loss of oxygen from a substance
32
What is oxidation (in terms of oxygen)?
The gain of oxygen by a substance
33
Which substance is the reducing agent?
The agent that gains oxygen (or any other substance) at the end of the reaction reaction
34
Which substance is the oxidising agent?
The substance that loses oxygen (or any other substance) at the end of a reaction
35
What happens to the ions of a substance that is oxidised?
It loses electrons
36
What happens to the ions of a substance that is reduced?
It gains electrons
37
What is a base?
A substance that neutralises acid
38
How do you know when a base is an alkali?
If it can dissolve in water
39
What substances are bases usually?
Metal oxides or metal hydroxides
40
What does a pH of lower than mean?
Acidic
41
What does a pH of 7 mean?
Neutral
42
What does a pH of above 7 mean?
Alkaline
43
What is the neutralisation reaction?
Acid + base —> salt + water
44
How can you predict the first part of the name of a salt in a neutralisation reaction?
The first part comes from the metal in the base or alkali except when ammonia or ammonium carbonate is used - the name of the salt starts with ammonium
45
How can you predict the second part of the name of a salt in a neutralisation reaction?
It comes from the acid used
46
What is the equation for when acids react with carbonates?
Acid + carbonate —> salt + water + carbon dioxide
47
What are carbonates?
Ionic compounds that contain the carbonate ion (CO3)2- where 2- is the charge
48
What is the formula for when acids react with metals?
Acid + metal —> salt + hydrogen
49
What is a dilute acid?
Contains a low ratio of acid to the volume of the solution
50
What is a concentrated acid?
Contains a high ratio of acid to the volume of the solution
51
What are weak acids?
They are partially ionised (only a fraction of their molecules release H+ ions)
52
What are strong acids?
Fully ionised (all the molecules release H+ ions)
53
How is pH linked to hydrogen ion concentration?
In an aqueous solution, as the concentration of H+ ions increases by a factor of 10, the pH decreases by 1
54
What is electrolysis?
A process in which an electric current is passed though a compound, causing a chemical change
55
What is an electrode?
A substance made from metal or graphite that conducts electricity to the electrolyte
56
What are the components of electrolysis?
An electrolyte 2 electrodes An electrical supply (power pack or battery)
57
What happens during electrolysis?
Positive ions gain electrons at the cathode to become atoms Negative ions lose electrons at the anode to become atoms
58
What is the cathode?
The negative electrode
59
What is the anode?
The positive electrode
60
What are cations?
Positive ions that go to the cathode
61
What are anions?
Negative ions that go the anode
62
What happens if the atoms formed by electrolysis are non-metals?
Covalent bonds may form between them, making molecules.
63
What happens when ions become atoms or molecules at the electrode?
You say that the ion has been discharged
64
What happens to the concentration of ions close to each electrode and why?
The concentration goes down as ions lose or gain electrons to become atoms
65
What are inert electrodes used for?
The electrolysis of many ionic compounds in their liquid state or in aqueous solution
66
What are inert electrodes usually made from?
Copper Platinum Graphite
67
What is produced at the cathode?
Hydrogen unless ions from a less reactive metal than hydrogen are present - that metal is produced instead
68
What metals are less reactive than hydrogen?
Copper Silver Gold Platinum
69
What is produced at the anode?
Oxygen unless ions from an element in group 7 are present at a high enough concentration
70
What is electroplating?
A type of electrolysis that uses non-inert electrodes with these electrodes changing during electrolysis
71
What is everything labelled as in electroplating?
The cathode is the object you want to coat The anode is a piece of the metal you want to coat the object with The electrolyte is a solution containing ions of the coating metals
72
How does electroplating work?
Metal ions from the electrolyte are discharged in the surface of the object (cathode). These ions are replaced by the metal ions leaving the surface of the anode until the whole anode is used up.
73
What is the half equation for the ion at the anode?
X is the ion X —> X+ + E- Make sure to include state symbols
74
What is the half equation for the ion at the cathode?
X is the ion X+ + E- —> X Make sure to include state symbols
75
What happens if you try electroplating an impure object?
Impurities collect underneath the anode

Chemistry (8 decks)

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