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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
Q

How much energy is required in endothermic reactions?

A

The amount of energy transferred to break bonds is MORE than the energy transferred when new bonds form

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26
Q

What is the energy change in exothermic reactions?

A

Positive - overall, energy is transferred from the surroundings which cool down

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27
Q

What does an endothermic reaction look like on a reaction profile?

A

High activation energy with products having more energy than reactants

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28
Q

What is the overall transfer of energy in an exothermic reaction?

A

The amount of energy transferred to break bonds is LESS than the energy transferred when new bonds form

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29
Q

What is activation energy?

A

The minimum energy needed for a reaction to start

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30
Q

What is a redox reaction?

A

A reaction in which reduction and oxidation happen at the same time

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31
Q

What is reduction (in terms of oxygen)?

A

The loss of oxygen from a substance

32
Q

What is oxidation (in terms of oxygen)?

A

The gain of oxygen by a substance

33
Q

Which substance is the reducing agent?

A

The agent that gains oxygen (or any other substance) at the end of the reaction reaction

34
Q

Which substance is the oxidising agent?

A

The substance that loses oxygen (or any other substance) at the end of a reaction

35
Q

What happens to the ions of a substance that is oxidised?

A

It loses electrons

36
Q

What happens to the ions of a substance that is reduced?

A

It gains electrons

37
Q

What is a base?

A

A substance that neutralises acid

38
Q

How do you know when a base is an alkali?

A

If it can dissolve in water

39
Q

What substances are bases usually?

A

Metal oxides or metal hydroxides

40
Q

What does a pH of lower than mean?

A

Acidic

41
Q

What does a pH of 7 mean?

A

Neutral

42
Q

What does a pH of above 7 mean?

A

Alkaline

43
Q

What is the neutralisation reaction?

A

Acid + base —> salt + water

44
Q

How can you predict the first part of the name of a salt in a neutralisation reaction?

A

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
Q

How can you predict the second part of the name of a salt in a neutralisation reaction?

A

It comes from the acid used

46
Q

What is the equation for when acids react with carbonates?

A

Acid + carbonate —> salt + water + carbon dioxide

47
Q

What are carbonates?

A

Ionic compounds that contain the carbonate ion (CO3)2- where 2- is the charge

48
Q

What is the formula for when acids react with metals?

A

Acid + metal —> salt + hydrogen

49
Q

What is a dilute acid?

A

Contains a low ratio of acid to the volume of the solution

50
Q

What is a concentrated acid?

A

Contains a high ratio of acid to the volume of the solution

51
Q

What are weak acids?

A

They are partially ionised (only a fraction of their molecules release H+ ions)

52
Q

What are strong acids?

A

Fully ionised (all the molecules release H+ ions)

53
Q

How is pH linked to hydrogen ion concentration?

A

In an aqueous solution, as the concentration of H+ ions increases by a factor of 10, the pH decreases by 1

54
Q

What is electrolysis?

A

A process in which an electric current is passed though a compound, causing a chemical change

55
Q

What is an electrode?

A

A substance made from metal or graphite that conducts electricity to the electrolyte

56
Q

What are the components of electrolysis?

A

An electrolyte
2 electrodes
An electrical supply (power pack or battery)

57
Q

What happens during electrolysis?

A

Positive ions gain electrons at the cathode to become atoms
Negative ions lose electrons at the anode to become atoms

58
Q

What is the cathode?

A

The negative electrode

59
Q

What is the anode?

A

The positive electrode

60
Q

What are cations?

A

Positive ions that go to the cathode

61
Q

What are anions?

A

Negative ions that go the anode

62
Q

What happens if the atoms formed by electrolysis are non-metals?

A

Covalent bonds may form between them, making molecules.

63
Q

What happens when ions become atoms or molecules at the electrode?

A

You say that the ion has been discharged

64
Q

What happens to the concentration of ions close to each electrode and why?

A

The concentration goes down as ions lose or gain electrons to become atoms

65
Q

What are inert electrodes used for?

A

The electrolysis of many ionic compounds in their liquid state or in aqueous solution

66
Q

What are inert electrodes usually made from?

A

Copper
Platinum
Graphite

67
Q

What is produced at the cathode?

A

Hydrogen unless ions from a less reactive metal than hydrogen are present - that metal is produced instead

68
Q

What metals are less reactive than hydrogen?

A

Copper
Silver
Gold
Platinum

69
Q

What is produced at the anode?

A

Oxygen unless ions from an element in group 7 are present at a high enough concentration

70
Q

What is electroplating?

A

A type of electrolysis that uses non-inert electrodes with these electrodes changing during electrolysis

71
Q

What is everything labelled as in electroplating?

A

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
Q

How does electroplating work?

A

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
Q

What is the half equation for the ion at the anode?

A

X is the ion
X —> X+ + E-
Make sure to include state symbols

74
Q

What is the half equation for the ion at the cathode?

A

X is the ion
X+ + E- —> X
Make sure to include state symbols

75
Q

What happens if you try electroplating an impure object?

A

Impurities collect underneath the anode

Chemistry (8 decks)

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