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C4 Flashcards

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1
Q

What metals react with oxygen what do they produce?

A
  • Metals react with oxygen to produce metal oxides
  • The reactions are oxidation reactions because the metals gain oxygen
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2
Q

What is reduction?

A
  • Reduction is the loss of oxygen
  • If a substance loses oxygen during a reaction, this is known as reduction
  • An example of this is a metal being extracted from an oxidised state
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3
Q

What is oxidation?

A
  • Oxidation is the loss of electrons from a substance
  • It is also the gain of oxygen by a substance
  • For example, magnesium is oxidised when it reacts with oxygen to form magnesium oxide: magnesium + oxygen → magnesium oxide
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4
Q

What metals react with other substances what so they form?

A

The metal atoms form positive ions

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5
Q

What is the reactivity of a metal related to?

A

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

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6
Q

How are metals arranged?

A
  • Metals can be arranged in order of their reactivity in a reactivity series
  • The metals potassium, sodium, lithium, calcium, magnesium, zing, iron and copper can be put in order of their reactivity from their reactions with water and dilute acids
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7
Q

Which non-metals are included in the reactivity series?

A

Hydrogen and carbon

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8
Q

What can a more reactive metal do?

A

A more reactive metal can displace a less reactive metal from a compound

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9
Q

Note:

A

AQA says that students should be able to:

• recall and describe the reactions, if any, of potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper with water or dilute acids and where appropriate, to place these metals in order of reactivity
• explain how the reactivity of metals with water or dilute acids is related to the tendency of the metal to form its positive ion
• deduce an order of reactivity of metals based on experimental results.

(Check CGP Page 133)

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10
Q

What are the reactions of metals with water and acids limited to?

A

Room temperature and do not include reactions with steam

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11
Q

How are most metal found in earth?

A

Unreactive metals such as gold are found in the Earth as the metal itself but most metals are found as compounds that require chemical reactions to extract the metal

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12
Q

How are metals less reactive than carbon extracted?

A

Their oxides by reduction with carbon

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13
Q

What does reduction involve?

A

The loss of oxygen

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14
Q

What does the reduction of oxides using carbon involve?

A
  • Carbon reduction reactions form two products
  • During a carbon reduction reaction, the metal ore loses oxygen whilst the carbon gains oxygen, forming carbon dioxide
  • For the metal ore to be extracted using carbon it needs to be less reactive than carbon in the reactivity series
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15
Q

Note:

A

AQA says that students should be able to:

• interpret or evaluate specific metal extraction processes when given appropriate information
• identify the substances which are oxidised or reduced in terms of gain or loss of oxygen.

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16
Q

What is oxidation?

A

Oxidation is the loss of electrons and reduction is the gain of electrons

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17
Q

Note:

A

AQA says that students should be able to:

  • write ionic equations for displacement reactions
  • identify in a given reaction, symbol equation or half equation which species are oxidised and which are reduced
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18
Q

When acids react with metals what do they produce?

A

Salts and hydrogen

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19
Q

What are redox reactions?

A
  • A redox reaction involves the transfer of electrons
  • During a redox reaction, there is a gain of electrons in one molecule and loss of electrons in another
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20
Q

Note:

A

AQA says that students should be able to:

• explain in terms of gain or loss of electrons, that these are redox reactions
• identify which species are oxidised and which are reduced in given chemical equations.
• Knowledge of reactions limited to those of magnesium, zinc and iron with hydrochloric and sulfuric acids.

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21
Q

Reactions of magnesium, zinc and iron with hydrochloric and sulfuric acids.

A
  • Acid + metal → salt + hydrogen

For example:
- Hydrochloric acid + magnesium → magnesium chloride + hydrogen
- Zinc and iron also react with hydrochloric acid
Magnesium, zinc and iron also react with sulfuric acid.
- sulfuric acid + iron → iron(II) sulfate + hydrogen

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22
Q

How are acids neutralised?

A

Acids are neutralised by alkalis (eg soluble metal hydroxides) and bases (eg insoluble metal hydroxides and metal oxides) to produce salts and water, and by metal carbonates to produce salts, water and carbon dioxide

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23
Q

What does a particular salt produced in any reaction between an acid and a base or alkali depend on?

A
  • The acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates)
  • The positive ions in the base, alkali or carbonate
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24
Q

Note:

A

AQA says that students should be able to:

  • predict products from given reactants
  • use the formulae of common ions to deduce the formulae of salts
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25
What are soluble salts made from?
- Soluble salts can be made from acids by reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides or carbonates - The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt
26
How do salt solutions produce solid salts?
By crystallising the salt solutions
27
Note:
AQA says that students should be able to describe how to make pure, dry samples of named soluble salts from information provided
28
Practical 8
AAAA
29
In aqueous solutions what do acids produce?
Hydrogen ions (H+)
30
In aqueous solutions of alkalis what do they contain?
Hydroxide ions (OH-)
31
What is the PH scale and what does it measure?
The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution, and can be measured using universal indicator or a pH probe
32
What is a neutral solution (pH)?
- A solution with pH 7 is neutral - Aqueous solutions of acids have pH values of less than 7 and aqueous solutions of alkalis have pH values greater than 7
33
What happens in neutralisation reactions between an acid and alkali?
In neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water This reaction can be represented by the equation: H+(aq) + OH-(aq) --> H20(l)
34
Note:
AQA says that students should be able to: • describe the use of universal indicator or a wide range indicator to measure the approximate pH of a solution • use the pH scale to identify acidic or alkaline solutions.
35
What is the characteristics of a strong acid?
A strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids.
36
What is the characteristics of a weak acid?
- A weak acid is only partially ionised in aqueous solution - Examples of weak acids are ethanoic, citric and carbonic acids
37
The stronger an acid...?
For a given concentration of aqueous solutions, the stronger an acid, the lower the pH
38
What happens when the pH decreased by 1 unit?
As the pH decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 10
39
What does dilute mean?
A dilute solution contains a relatively small amount of dissolved solute
40
What does concentrated mean?
A concentrated solution contains a relatively large amount of dissolved solute
41
What does weak mean in terms of ionisation?
- If an acid is weak, that means it will be partially ionised in an aqueous solution - Only some particles dissociate to release H+ ions, meaning this reaction is a reversible reaction
42
What does strong mean in terms of ionisation?
- Strong acids are completely ionised - If an acid is strong, that means it will be completely ionised in an aqueous solution
43
Note:
AQA says that students should be able to describe neutrality and relative acidity in terms of the effect on hydrogen ion concentration and the numerical value of pH (whole numbers only).
44
What happens when an ionic compound is melted or dissolved in water?
- When an ionic compound is melted or dissolved in water, the ions are free to move about within the liquid or solution - These liquids and solutions are able to conduct electricity and are called electrolytes
45
What happens when an electric current passes through electrolytes?
- Passing an electric current through electrolytes causes the ions to move to the electrodes - Positively charged ions move to the negative electrode (the cathode), and negatively charged ions move to the positive electrode (the anode) - Ions are discharged at the electrodes producing elements - This process is called electrolysis
46
What is electrolysis?
- Electrolysis is the decomposition of an electrolyte by an electric current - It is used to extract reactive metals from their ores - Electrolysis needs: a dc electrical supply - A negative electrode , called a cathode
47
Note:
AQA says that students should be able to write half equations for the reactions occurring at the electrodes during electrolysis, and may be required to complete and balance supplied half equations.
48
What happens when a simple ionic compound (eg lead bromide) is electrolysed in the molten state using inert electrodes?
When a simple ionic compound (eg lead bromide) is electrolysed in the molten state using inert electrodes, the metal (lead) is produced at the cathode and the non-metal (bromine) is produced at the anode
49
Note:
AQA says that students should be able to predict the products of the electrolysis of binary ionic compounds in the molten state.
50
How can metal be extracted from molten compounds?
- Metals can be extracted from molten compounds using electrolysis - Electrolysis is used if the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon - Large amounts of energy are used in the extraction process to melt the compounds and to produce the electrical current
51
How is aluminium is manufactured by the electrolysis?
Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the positive electrode (anode)
52
Explain why a mixture is used as the electrolyte
- The mixture of cryolite and aluminium oxide has a lower melting point than pure aluminium oxide - This means a lower amount of energy is required to establish effective conditions for electrolysis and thus makes it more cost effective
53
Explain why the positive electrode must be continually replaced
The positive electrode (anode) is made of carbon, which reacts with the oxygen to produce carbon dioxide and so must be continually replaced
54
What do the ions discharged when an aqueous solution is electrolysed using inert electrodes depend on
The relative reactivity of the elements involved
55
What is produced at the negative electrode?
At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen
56
What is produced at the positive electrode?
At the positive electrode (anode), oxygen is produced unless the solution contains halide ions when the halogen is produced
57
Why is oxygen produces in the positive electrode?
This happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are discharged
58
Note:
AQA says that students should be able to predict the products of the electrolysis of aqueous solutions containing a single ionic compounds
59
Practical 9
AAAA
60
What happens during electrolysis at the cathode?
During electrolysis, at the cathode (negative electrode), positively charged ions gain electrons and so the reactions are reductions
61
What happens at the anode during electrolysis?
At the anode (positive electrode), negatively charged ions lose electrons and so the reactions are oxidations
62
Reactions at electrodes can be represented by...? (Show some examples)
Reactions at electrodes can be represented by half equations, for example: 2H+ + 2e- -> H2 and 4OH- -> O2 + 2H2O + 4e- Or 4OH- - 46- - O2 + 2H2O
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