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chemical changes Flashcards

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1
Q

What are the two definitions of oxidation?

A

Oxidation is the loss of electrons.

Oxidation is the gain of oxygen.

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2
Q

What are the two definitions of reduction?

A

Reduction is the gain of electrons.

Reduction is the loss of oxygen.

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3
Q

What is a redox reaction?

A

A redox reaction is when oxidation and reduction happen simultaneously.

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4
Q

What is the reactivity series?

A 
potassium
sodium
lithium
calcium 
magnesium
(carbon)
zinc
iron
(hydrogen)
copper
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5
Q

What is the reactivity of metals related to?

A

The reactivity of metal is related to its tendency to form positive ions.

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6
Q

How does the reactivity series react with water?

A

with water:

  • potassium, sodium and lithium - very rapid
  • calcium - quite rapid
  • magnesium, zinc, iron and copper - no reaction
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7
Q

How does the reactivity series react with dilute acid?

A

with dilute acid:

  • potassium, sodium and lithium - dangerously fast
  • calcium - extremely vigorous
  • magnesium - rapid
  • zinc - quite rapid
  • iron - quite slow
  • copper - no reaction
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8
Q

What is the definition of an acid?

A

An acid will produce hydrogen ions (H+) in aqueous solutions.

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9
Q

What ions are sulfuric acid made up of?

A

H2SO4 is made up of 2H+ and (SO4)2-.

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10
Q

What are bases?

A

Bases are chemicals which can neutralise acids to produce salt and water. They are usually metal oxides or hydroxides.

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11
Q

What is another name for bases that are soluble in water?

A

Bases that are soluble in water are called alkalis.

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12
Q

What is the definition of an alkali?

A

Alkalis produce hydroxide ions (OH-) in aqueous solutions.

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13
Q

Give the equation for neutralisation.

A

H+ + OH- –> H2O

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14
Q

What is the pH for acids and alkalis?

A

acids - pH 1 - 6

alkalis - pH 8 - 14

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15
Q

What are two ways to measure pH?

A

A pH probe or a universal indicator.

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16
Q

What are the products from acid + metal?

A

acid + metal –> salt + hydrogen

17
Q

What kind of salts does hydrochloric acid produce?

A

Hydrochloric acid produces salts ending in chloride.

18
Q

What kind of salts does sulfuric acid produce?

A

Sulfuric acid produces salts ending in sulfate.

19
Q

What kind of salts does nitric acid produce?

A

Nitric acid produces salts ending in nitrate.

20
Q

What are the products from acid + alkali OR base?

A

acid + alkali OR base –> salt + water

21
Q

What are the products from acid + metal carbonate?

A

acid + metal carbonate –> salt + water + carbon dioxide

carbonate is (CO3)2-

22
Q

What is a strong acid? Give examples.

A

Strong acids fully ionise in aqueous solutions.

Examples are hydrochloric, nitric and sulfuric acid.

23
Q

What is a weak acid? Give examples.

A

Weak acids partially ionise in aqueous solutions.

Examples are carbonic acid, ethanolic acid and citric acid.

24
Q

What does each unit of the pH scale represent?

A

As the pH scale decreases by 1, the concentration of hydrogen ions increases by 10x.

25
Q

What happens during electrolysis?

A

During electrolysis, an electric current is passed through the melted or aqueous ionic compound (electrolyte), and the ions are attracted to an electrode (a solid that can conduct electricity, graphite or metal).

+ metal ions go to the cathode (negative) and gain electrons
- non-metal ions go to the anode (positive) and lose electrons
This creates a flow of charge.

26
Q

What is the order of discharge for electrolysis at the anode and cathode?

A

anode - Ag+ > Cu+ > H+ > other

cathode - Cl-, Br- > OH- > other

27
Q

Why do we not use metals less reactive than carbon in electrolysis?

A

As they can be extracted by reduction with carbon, which is much cheaper.

28
Q

Where is aluminium extracted from?

A

Aluminium is extracted from its ore, bauxite, Al2O3. Mixed with cryolite to lower melting point when extracted.

29
Q

What are the half equations at each electrode for the extraction of aluminium from Al2O3?

A

anode - 202- –> O2 + 4e-

cathode - Al3+ + 3e- –> Al

30
Q

Why must the anode be replaced regularly?

A

The anode must be replaced regularly as O2 reacts with carbon on the electrode to form CO2.

31
Q

In aqueous solutions, how do the water molecules ionise at each electrode?

A

anode - 4OH- –> O2 + 2H2O + 4e-

cathode - 2H+ + 2e- –> H2

y chemistry paper one (6 decks)

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