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Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

1
Q

List the reactivity series.

A

Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Hydrogen
Copper
Silver
Gold

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2
Q

What happens when a metal reacts with water?

A

Metal + water → metal hydroxide + hydrogen

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3
Q

What happens when a metal reacts with a dilute acid?

A

A salt and hydrogen are formed.

E.g. Magnesium + hydrochloric acid → magnesium chloride + hydrogen

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4
Q

How would a metal below hydrogen react with a dilute acid?

A

It wouldn’t be able to react.

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5
Q

What is oxidation and reduction?

A

Oxidation
Is
Loss
Reduction
Is
Gain
of electrons

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6
Q

What is a displacement reaction?

A

When an more reactive metal displaces a less reactive metal from its compound.

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7
Q

What kind of reaction is electrolysis?

A

Displacement

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8
Q

Evaluate the differences between reduction by carbon and electrolysis.

A

Reduction by carbon can only be done if the metal is less reactive than carbon. Electrolysis is used if the metal is more reactive however it is more expensive as it uses electrical energy.

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9
Q

Why is aluminium so expensive?

A

Electrolysis is used to extract it.

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10
Q

What state do the electrolytes in electrolysis need to be in?

A

Molten or dissolved in water

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11
Q

Why does aluminium have to be molten?

A

It is insoluble

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12
Q

Why is aluminium oxide dissolved in cryolite?

A

The melting point of aluminium oxide is high so a lot of energy must be transferred to break its strong ionic bonds, and this is expensive and cryolite melts at a lower temperature.

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13
Q

What happens at the cathode and anode during the electrolysis of aluminium?

A
  • Cathode: aluminium ions are reduced to form aluminium atoms. Al3+ + 3e- → Al
  • Anode: oxide ions are oxidised and form oxygen gas. 2O2- → O2 + 4e-
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14
Q

What do acids form in aqueous solutions?

A

Hydrogen ions - H+

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15
Q

What do alkalis form in aqueous solutions?

A

Hydroxide ions - OH-

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16
Q

How can the pH of a solution be measured?

A
  • Universal indicator Red — Green — Blue
  • Blue litmus paper Red — Blue — Blue
17
Q

What is base?

A

Any substance that reacts with an acid to form a salt and water.

18
Q

What is a salt?

A

The substance formed when the hydrogen ion in an acid is replaced by a metal ion.

19
Q

What is an alkali?

A

A soluble base.

20
Q

What is a neutralisation reaction?

A

A reaction between an acid and a base.

21
Q

What is the equation for a neutralisation reaction?

A

H+(aq) + OH-(aq) → H2O(l)

22
Q

What forms when an acid reacts with a metal?

A

Acid + metal → salt + hydrogen

23
Q

What is the equation for when a metal oxide reacts with acid?

A

Acid + metal oxide → salt + water

24
Q

What is the reaction when an acid reacts with carbonates?

A

Acid + carbonate → salt + water + carbon dioxide

25
Q

How is a salt named?

A

The base, alkali or carbonate is the first section and the second section is the acid.
E.g. Hydrochloric acid produces chloride salt

26
Q

How can a soluble salt be formed?

A

By reacting an acid with an insoluble reactant (e.g. a metal, a metal oxide, a metal hydroxide or a carbonate).

27
Q

How do you make a soluble salt from an acid and an insoluble reactant?

A
  1. Add powdered insoluble reactant to acid in a beaker until it is in excess.
  2. Filter the mixture in the beaker to remove the excess solid. The filtrate now contains only the salt and water.
  3. Heat the solution in an evaporating dish over a water bath. Until small crystals start to appear - the solution is now saturated.
  4. Leave the saturated solution at room temperature for a day or two. This gives time for large crystals to form.
28
Q

When does a solution form?

A

When a solute dissolves in a solvent.

29
Q

What is the difference between strong acids and weak acids?

A

String acids completely dissociate into ions whilst weak acids only partially dissociate.

30
Q

What is pH?

A

A measure of its concentration of hydrogen ions.

The higher the concentration of H+ ions in an acidic solution, the lower the pH
the lower the concentration of H+ ions in an acidic solution, the higher the pH

31
Q

What are examples of strong and weak acids?

A
  • Nitric acid
  • Sulphuric acid
  • Hydrochloric acid
  • Citric acid
32
Q

What is the electrolyte?

A

A substance that conducts an electrical current when in the molten state or is dissolved in water.

33
Q

What is electrolysis?

A

The decomposition of a compound using an electric current.

34
Q

Cations are …

A

Pawsitive (positive)

35
Q

Anions are …

36
Q

What forms at the anode and cathode during the electrolysis of dissolved ionic compounds?

A

Cathode: the metal is produced if it is less reactive than hydrogen
Anode: oxygen is produced unless valued ions are present

37
Q

What is the layout for half equations at the cathode and anode?

A

Cathode: Na+ + e- → Na
Anode: 2Cl- → Cl2 + 2e-

Chemistry (10 decks)

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