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Chemistry AQA > C4 Chemical Change > Flashcards

C4 Chemical Change Flashcards

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1
Q

What is oxidation/reduction?

A

Oxidation - When a substance gains oxygen
Reducation - When a substance loses oxygen

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2
Q

What is the reactivity series of metals? What are the trends in reactivities of metals ni reactions with acids/water?

A

The series shows the metals in order of their reactivity.

Metals above H2 in reactivity series react with acid to produce H2. The more reactive the metal is, the quicker and more violent reaction with acid occurs.

Metals below H, don’t react with acids.

Not all metals above H2 react with water - mostly Group I and II metals. Aluminium is the borderline case.

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3
Q

What is a displacement reaction?

A

A reaction where a more reactive metal displaces a less reactive metal from a compound

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4
Q

How are unreactive metals found in Earth?

A

In their natural state (well, they are unreactive…)

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5
Q

How are metals more reactive than carbon extracted?

A

By electrolysis

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6
Q

How can metals less reactive than carbon be extracted?

A

Reduction with carbon. Carbon displaces the metal ni a metal oxide - gets oxidised to carbon oxides. Metal from hte metal oxide gets reduced to the pure metal.

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7
Q

What is the general equation for a reaction between metals and acids? What type of reaction is this?

A

Metal + acid → salt + hydrogen
Redox reaction, also a displacement reaction

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7
Q

How are oxidation and reduction defined in terms of electron transfer?

A

(OILRIG)

Oxidation - loss of electrons Reduction - gain of electrons

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8
Q

Which metals in the reactivity series will react with acid?

A

Those above hydrogen

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9
Q

What is the general equation for a neutralisation reaction?

A

Base + acid → salt + water

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10
Q

What is the general equation for the reaction between metal carbonate and acid?

A

Metal carbonate + acid → salt + water + carbon dioxide

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11
Q

What is the general equation for the reaction between metal oxides and acids?

A

Metal oxide + acid → a salt + water

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12
Q

What is a redox reaction?

A

A reaction where both oxidation and reduction occurs

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13
Q

Explain in terms of gain or loss of electrons which species has been oxidised and which species has been reduced when magnesium reacts with hydrochloric acid

A

Magnesium has lost electrons and thus has been oxidised (Mg to Mg2+)
The hydrogen in HCl has gained electrons and thus has been reduced (H+ to H2)

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14
Q

How is a soluble salt formed?

A

a) React the excess acid with some insoluble chemical (e.g. metal oxide)
b) Filter of the leftovers
c) Crystallise the product

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15
Q

What do acids and alkalis produce in aqueous solutions?

A

Acids produce hydrogen ions, alkalis produce hydroxide ions

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16
Q

What are bases, acids and alkalis?

A

Bases are compounds that neutralise acids, acids produce hydrogen ions in aqueous solutions, alkalis are soluble bases - produce hydroxide ions in aqueous solutions

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17
Q

What is the pH scale and what does a pH of 7 show?

A

The measure of acidity/alkalinity of a solution; neutral solution

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18
Q

State the general equation for a neutralisation reaction ni a short, ionic form.

A

Н+ + ОН- → Н20

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19
Q

What is a strong acid and weak acid?

A

Strong acid is completely ionised in aqueous solution; weak acid is only partially ionised in aqueous solution

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20
Q

What happens to pH as concentration of H+ increases?

A

The pH decreases

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21
Q

Name the folowing salts: LiNO3, K2CO3, MgBr2, BaSO4

A

Lithium nitrate
Potassium carbonate
Magnesium bromide
Barium sulfate

22
Q

What is a concentrated acid and what is a diluted acid? Is this the same as a strong and weak acid?

A
  • Concentrated acid has more moles of acid per unit volume than dilute (dilute refers to solutions of low concentrations)
  • It is not the same - concentration is not the same thing as strength of an acid.
  • Strength refers to whether the acid is completely ionised in water (strong) or only partially (weak).
23
Q

As the ph is decreased by one unit, what change si seen ni the hydrogen ion concentration?

A

Increases by a factor of 10

24
Q

What is electrolysis?

A

The passing of an electric current through ionic substances that are molten or in solution to break them down into elements; ions are discharged (they lose/gain electrons) at electrodes to produce these

25
Q

What is an electrolyte?

A

The liquid/solution which conducts electricity

26
Q

What occurs at the cathode and what occurs at the anode during electrolysis?

A

Reduction occurs at the cathode Oxidation occurs at the anode

27
Q

What is a cathode and what is an anode?

A

Cathode is the negative electrode, anode is the positive electrode

28
Q

In aqueous electrolysis, which element is discharged at the cathode? Oxygen is produced at the anode unless what?

A

The less reactive element discharges at the cathode. Hydrogen is produced unless there is a less reactive metal, ni which case the said metal si produced. Oxygen is produced at the anode unless the solution contains halide ions, ni which case halogen molecules are produced.

29
Q

How is aluminium manufactured?
Why is it expensive?

A

Aluminium is made through the electrolysis of aluminium oxide and cryolite.

Lots of energy is needed ot produce the current ni electrolysis which makes this process expensive.

30
Q

What are the half equations ni the extraction of aluminium?

A

Al3+ + 3 e- → Al (cathode)
2 02- → O2 + 4 e- (anode)

Oxygen reacts with C of the anode producing CO2-.

31
Q

Why is cryolite used in manufacturing of aluminium?

A

It lowers the melting point of aluminium oxide, reducing energy costs

32
Q

What are the half equations in electrolysis of the aqueous Na2SO4?

A

2 H+ + 2 e- →H2 (cathode)
4 OH- → 2 H20 + O2 +4 e- (anode)

33
Q

What are the half equations in electrolysis of the molten and aqueous KCI?

A

K+ + e- → K (cathode)
2 Cl- →Cl2 +2 e- (anode)
2 H+ + 2 e- → H2 (cathode)
2 CI → CI2 + 2 e- (anode), respectively

34
Q

What are the half equations in electrolysis of the aqueous CuBr2?

A

Cu2+ + 2 e- → Cu (cathode)
2Br → Br2 + 2 e- (anode)

35
Q

Acid:

A

​Acids produce hydrogen ions (H+​)​ in aqueous solutions. They have a pH range of 0-6.

36
Q

Alkali:

A

Alkalis produce hydroxide ions (OH-​ )​ in aqueous solutions. They have a pH range of 8-14.

36
Q

Filtration:

A

​A separation technique used to separate solids from liquids.

37
Q

Displacement:

A

​A chemical reaction in which a more reactive element displaces a less reactive element from its compound.

38
Q

Crystallisation:

A

​A separation technique used to produce solid crystals from a solution by evaporating the solvent.

39
Q

Extraction:

A

Extraction techniques are used to separate a desired substance when it is mixed with others.

40
Q

Electrolysis:​

A

​The splitting up of an ionic compound using electricity.​ The electric current is passed through a substance causing chemical reactions at the electrodes and the decomposition of the materials.

41
Q

Electrolyte:

A

​A solution containing free ions from the molten or dissolved ionic substance. The ions are free to move to carry charge.

42
Q

Negative electrode (cathode):

A

​The electrode where hydrogen is produced if the metal in the electrolyte is more reactive than hydrogen. ​It is where positively charged ions gain electrons and so the reactions are reductions.

42
Q

Neutralisation:

A

The reaction ​when an acid and a base react to form water and a salt.

43
Q

Oxidation:

A

A reaction involving the gain of oxygen. ​Oxidation is the loss of electrons.

44
Q

pH scale:

A

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.

45
Q

Positive electrode (anode):

A

​The electrode where oxygen is produced unless the solution contains halide ions then the halogen is produced. ​It is where negatively charged ions lose electrons and so the reactions are oxidations.

46
Q

Reduction:

A

A reaction involving the loss of oxygen. ​Reduction is the gain of electrons.

46
Q

Strong acid:

A

A strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids.

47
Q

Reduction with carbon:

A

​Metals less reactive than carbon can be extracted from their oxides by reduction with carbon.

48
Q

The reactivity series:

A

​Metals are arranged in order of their reactivity in a reactivity series. This can be used to predict products from reactions.

49
Q

Universal indicator:

A

A mixture of dyes that changes colour gradually over a range of pH and is used in testing for acids and alkalis.

50
Q

Weak acid:

A

A weak acid is only partially ionised in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids.

Chemistry AQA (5 decks)

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