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CHEMISTRY Questions > C4 Chemical changes > Flashcards

C4 Chemical changes Flashcards

1
Q

What is the reactivity series?

A

A list of metals ordered by their reactivity

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2
Q

How can the order of reactivity for specific metals be found?

A

Add the metals to water or acid and see which ones react the most (by how much fizzing there is)

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3
Q

What is the name for a reaction where oxygen is added to form a compound?

A

Oxidation

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4
Q

What is the name for a reaction where oxygen is removed from a compound?

A

Reduction

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5
Q

Which is metal in the reactivity series is the first one that doesn’t react with acid?

A

Copper as it is less reactive than hydrogen

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6
Q

Explain why zinc can be extracted from zinc oxide with carbon but magnesium cannot be extracted from magnesium oxide with carbon

A

Magnesium is more reactive than carbon (1), Zinc is less reactive than carbon (1), Carbon can therefore remove oxygen from zinc oxide but not magnesium oxide (1)

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7
Q

Explain why gold and silver can be found pure in the Earth’s crust

A

They are very unreactive

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8
Q

What process is used to extract metals less reactive than carbon?

A

Reduction with carbon

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9
Q

Which metals are extracted by reduction with carbon?

A

Iron, Zinc and Copper

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10
Q

What process is used to extract metals more reactive than carbon?

A

Electrolysis

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11
Q

Define an ore

A

A rock containing enough metal in it for it to be economically worthwhile to extract the metal.

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12
Q

Define a displacement reaction

A

A reaction in which a more reactive element takes the place of a less reactive element

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13
Q

Define oxidation in terms of electrons

A

Oxidation is the loss of electrons

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14
Q

Define reduction in terms of electrons

A

Reduction is the gain of electrons

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15
Q

Which of the substances below has been oxidized and which has been reduced? Al³⁺ + Fe → Fe³⁺ + Al

A

Aluminium has been reduced and iron has been oxidised

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16
Q

Show two half equations for the reaction below: Al³⁺ + Fe → Fe³⁺ + Al

A

Al³⁺ + 3e⁻ → Al, Fe → Fe³⁺ + 3e-

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17
Q

Define acid in terms of pH

A

A substance with a pH of less than 7

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18
Q

Define acids in terms of ions

A

A substance which releases H⁺ ions in solution

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19
Q

What does (aq) stand for?

A

Aqueous: when something is dissolved in water. E.g. NaCl(aq) is salt water

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20
Q

State the three common acids and give their formulae

A

Hydrochloric acid, HCl(aq), Sulphuric acid, H₂SO₄(aq), Nitric acid, HNO₃

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21
Q

What is the formula of the carbonate ion?

A

CO3^2-

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22
Q

What is the formula of the sulphate ion?

A

SO4^2-

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23
Q

What is the formula of the nitrate ion?

A

NO3-

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24
Q

What is the fomula of the hydroxide ion?

A

OH-

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25
Q

What is a neutral solution?

A

A solution with a pH of 7. Water is an example.

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26
Q

How do you measure pH?

A

With an indicator or pH probe.

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27
Q

What is a base?

A

A metal oxide, hydroxide or carbonate that will react with an acid. E.g. copper oxide

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28
Q

What is an alkali?

A

A soluble base. E.g. sodium hydroxide

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29
Q

Which ions are always present in a solution of an alkali?

A

OH⁻

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30
Q

What is a salt?

A

An ionic compound formed during neutralisation

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31
Q

What type of salts are formed by the three main acids?

A

Hydrochloric acid produces chlorides, sulphuric acid = sulphates, nitric acid = nitrates

32
Q

What is a neutralisation reaction?

A

A reaction involving an acid that results in a neutral solution

33
Q

Which ions always react together in a neutralization reactions between acids and alkalis?

A

H⁺ and OH⁻

34
Q

Write the equation showing the reaction between H⁺ and OH⁻ ions

A

H⁺ + OH⁻ → H2O

35
Q

metal + acid →

A

→ salt + hydrogen gas

36
Q

metal hydroxide + acid →

A

→ salt + water

37
Q

metal oxide + acid →

A

→ salt + water

38
Q

metal carbonate + acid →

A

→ salt + water + carbon dioxide

39
Q

How do you make a pure salt from an acid?

A

React the acid with a excess base then filter off the excess base. E.g. to make copper sulphate react copper oxide with sulphuric acid

40
Q

If a salt is in solution, how do you extract it as a solid?

A

Allow the water to evaporate off and it will leave the salt behind as a solid.

41
Q

What is a strong acid?

A

An acid which completely ionises in water. E.g. when HCl is in water all the HCl molecules split up into H⁺ and Cl⁻

42
Q

What is a weak acid?

A

An acid which only partially ionises in water. E.g. in ethanoic acid only some of the molecules will have split up into the ethanoate ion and H⁺ ions.

43
Q

What is the relationship between the strength of an acid and its pH?

A

As an acid increases in strength the pH decreases.

44
Q

What is a concentrated acid?

A

An acid where there are lots of acid particles in the water.

45
Q

What is a dilute acid?

A

An acid where there are fewer acid particles in the water.

46
Q

What is pH a measure of?

A

pH is measure of concentration of H⁺ in a solution.

47
Q

If the pH increases by 1 what does this mean has happened to the H+ ion concentration?

A

It has decreased by a factor of 10

48
Q

How is a tritartion carried out?

A

An acid of known concentration is placed in a conical flask with a few drops of indicator. An alkali of unknown concentration is added in until there is a permanent colour change

49
Q

How can you make a titartion more accurate

A

Do a rough titration first, use a white tile to see the colour change better, add the alkali drop by drop near the end point and repeat it until you get consistent results.

50
Q

Which ions are in CaCO3

A

Ca2+ and CO32-

51
Q

Which ions are in Mg(OH)₂

A

Mg2+ and 2 ions of OH⁻

52
Q

What is the formula of iron (III) oxide?

A

Fe2O3

53
Q

What is the formula of sodium sulphate?

A

Na2SO4

54
Q

Is this process oxidation or reduction? Al → Al³⁺ + 3e⁻

A

Oxidation

55
Q

Is this process oxidation or reduction? Na⁺ + e⁻ → Na

A

Reduction

56
Q

What is electrolysis?

A

Using electricity to break down a substance

57
Q

What happens to an ionic substance when it is melted or dissolved in water?

A

The ions become free to move around

58
Q

What is an electrolyte?

A

A solution or liquid containing ions

59
Q

What is the name for the positive electrode?

A

The anode

60
Q

What is the name for the negative anode?

A

The cathode

61
Q

Which electrode do negative ions move to?

A

Cathode

62
Q

Which electrode do positive ions move to?

A

Anode

63
Q

Balance the equation: Al3+ + e⁻ → Al

A

Al3+ + 3e⁻ → Al

64
Q

Balance the equation: Cl⁻ → Cl2+ e⁻

A

2Cl⁻ → Cl2 + 2e⁻

65
Q

Balance the equation: O2- → O2 + e⁻

A

2O2- → O2 + 4e⁻

66
Q

What will be the products for the electrolysis of molten iron bromide?

A

Iron and bromine

67
Q

What will be the products for the electrolysis of molten zinc oxide?

A

Zinc and oxygen

68
Q

If electrolysis of a solution containing a metal more reactive than hydrogen is carried out what forms at the cathode?

A

Hydrogen

69
Q

If electrolysis of a solution containing sulphate, carbonate or nitrate ions what is produced at the anode?

A

Oxygen

70
Q

What is the main disadvantage of using electrolysis to extract metals?

A

Requires a large amount of energy to melt the compounds and to produce the necessary electricity

71
Q

Why is aluminium oxide mixed with cryolite when extracting aluminium?

A

To lower the melting point

72
Q

What is produced at the anode and cathode in the electrolysis of aluminium oxide?

A

Aluminium at the cathode and oxygen at the anode

73
Q

Why does the anode need to be replaced in the electrolysis of aluminium oxide?

A

The oxygen reacts with the carbon electrode to produce carbon dioxide.

74
Q

In the electrolysis of sodium chloride solution, what are the products?

A

Chlorine gas and hydrogen gas

75
Q

Why is sodium not produced in the electrolysis of sodium chloride solution?

A

It is more reactive than hydrogen so hydrogen is produced instead.

76
Q

In the electrolysis of lithium sulphate solution, what are the products?

A

Chlorine gas and oxygen gas

CHEMISTRY Questions (10 decks)

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