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Chemistry AQA Triple > Chemical Changes > Flashcards

Chemical Changes Flashcards

Paper 1 - C4

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1
Q

What happens when a metal reacts with oxygen?

A

We form a metal oxide and the metal atoms have been oxidised

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2
Q

What is gaining oxygen called?

A

An oxidation reaction

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3
Q

What is losing oxygen called?

A

A reduction reaction

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4
Q

How fast is the reaction with water at room temperature for potassium, sodium and lithium?

A

They react very rapidly

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5
Q

How fast is the reaction with water at room temperature for calcium?

A

Reacts quite rapidly

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6
Q

How fast is the reaction with water at room temperature for magnesium, zinc, iron and copper?

A

No reaction at all

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7
Q

What are the first 10 elements of the reactivity series in order starting from copper.

A

Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper

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8
Q

What does the ability to lose electrons and form a positive ion depend on?

A

The reactivity of the metal

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9
Q

Where are unreactive metals found?

A

In the Earth as the metal itself

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10
Q

What is a displacement reaction?

A

When a more reactive element will push out (displace) a less reactive element from its compound.

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11
Q

What is the formula for Hydrochloric acid?

A

HCl

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12
Q

What is the formula for Sulfuric acid?

A

H₂SO₄

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13
Q

What is the formula for Nitric acid?

A

HNO₃

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14
Q

What do acids produce in aqueous solutions?

A

Hydrogen ions (H+)

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15
Q

What do bases do?

A

Neutralise acids producing a salt and water

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16
Q

What are bases made up of?

A

Metal oxides or metal hydroxides

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17
Q

What are some examples of bases?

A

Copper oxide
Iron (III) hydroxide
Sodium hydroxide

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18
Q

What are bases which are soluble in water called?

A

Alkalis

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19
Q

What do alkalis produce in aqueous solutions?

A

Hydroxide ions (OH-)

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20
Q

What does the pH scale tell us?

A

The acidity or alkalinity of a solution

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21
Q

What pH do acids have?

A

A pH between 0 and 6

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22
Q

What are solutions with a pH of 7 called?

A

Neutral

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23
Q

What pH do alkalis have?

A

A pH between 8 and 14

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24
Q

How can we determine a pH of a soluton?

A

By using a pH probe or Universal indicator

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25
Q

How does a pH probe determine the pH?

A

It determines it electronically

26
Q

How does Universal indicator determine the pH?

A

Changes colour whether a solution is acid, alkali or neutral

27
Q

What colour shows a neutral solution (pH 7)?

A

Green

28
Q

What colour shows a Very acidic solution (pH 0)?

A

Red

29
Q

What colour shows a Very alkaline solution (pH 14)?

A

Purple

30
Q

What is the equation for Neutralisation?

A

H+ + OH- —–> H₂O

31
Q

What do all acids contain?

A

Hydrogen

32
Q

What do metals which react with Hydrochloric acid end with?

A
  • Chloride
33
Q

What do metals which react with Sulfuric acid end with?

A
  • Sulfate
34
Q

Why does magnesium react rapidly with acids?

A

Because its a lot more reactive than hydrogen

35
Q

Why does iron react fairly slowly with acids?

A

Because iron is only slightly more reactive than hydrogen

36
Q

What happens when acids react with a metal carbonate?

A

They make a salt, water and carbon dioxide

37
Q

What is a strong acid?

A

Strong acids fully ionise in aqueous solutions

38
Q

What are some examples of strong acids?

A

-Hydrochloric acid
-Sulfuric acid
-Nitric acid

39
Q

What is a weak acid?

A

Weak acids partially ionise in aqueous solutions

40
Q

What are some examples of weak acids?

A

-Carbonic acid
-Ethanoic acid
-Citric acid

41
Q

What has a lower pH strong or weak acids?

A

Strong acids

42
Q

Key fact for the pH scale:

A

As the pH scale decreases by one unit the concentration of hydrogen ions increases by ten times. And the pH scale also gives us an idea of the concentration of hydrogen ions.

43
Q

What does the concentration of an acid tell us?

A

The amount of acid molecules in a given volume of solution. And a dilute acid will have fewer acid molecules in a given volume than a concentrated acid even if the strength of the acid is the same.

44
Q

Why can solid ionic compound not conduct electricity?

A

Because the ions are locked in place and are not free to move

45
Q

What happens when the ionic compounds are melted or dissolved in water?

A

The forces of attraction are broken and the ions are free to move, and now the liquid can conduct electricity and scientists call these electrolytes.

46
Q

What is the negative electrode called?

A

Cathode

47
Q

What is the positive electrode called?

A

Anode

48
Q

What are the positive ions attracted to?

A

The negative electrode (cathode)

49
Q

What are the negative ions attracted to?

A

The positive electrode (anode)

50
Q

What is aluminium extracted by?

A

From the compound aluminium oxide by electrolysis

51
Q

Why is aluminium oxide mixed with cryolite in electrolysis?

A

To lower the melting point which reduces the amount of energy needed and saves money.

52
Q

What is the cathode and anode made out of?

A

Graphite (carbon)

53
Q

What is the half equation for electrolysis of aluminium oxide for the reduction reaction?

A

Al³+ + 3e- ——> Al
-Each ion gains three electrons and forms an aluminium atom

54
Q

What is the half equation for electrolysis of aluminium oxide for the oxidation reaction?

A

O²- —–> O + 2e-
-Each oxide ion loses 2 electrons to form an oxygen atom

55
Q

Why must the anode be replaced regularly?

A

Because the electrodes are made out of graphite and that’s a form of carbon.

56
Q

Why is electrolysis very expensive?

A

-Melting the compounds such as aluminium oxide requires a great deal of energy.
-A lot of energy is required to produce the electric current.

57
Q

What happens in electrolysis of aqueous solutions?

A

Water molecules ionise (split) forming hydrogen ions and hydroxide ions. And hydrogen is produced at the cathode if the metal is more reactive than hydrogen and in most cases oxygen gas is produced at the anode.

58
Q

Why is Platinum often used as an electrode?

A

Because its unreactive

59
Q

What are the half equations for Electrolysis of Copper sulfate solution?

A

Cathode:
Cu²+ + 2e- -Reduction—> Cu

Anode:
4OH- -Oxidation—> O₂ + 2H₂O + 4e-

60
Q

What happens if the aqueous solution contains halide ions?

A

The halogen will be produced at the anode

61
Q

What are the half equations of Electrolysis Sodium chloride solution?

A

Cathode:
2H+ + 2e- -Reduction—> H₂

Anode:
2Cl- -Oxidation—> Cl₂ + 2e-

Chemistry AQA Triple (17 decks)

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