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GCSE Chemistry > C2 - Salts & Electrolysis > Flashcards

C2 - Salts & Electrolysis Flashcards

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0
Q

What is an alkali?

A
  • A soluble hydroxide.

- Produce OH- ions when added to water.

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1
Q

What are acids?

A

Substances that produce H+ ions when added to water.

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2
Q

What are bases?

A

Substances which neutralise acids.

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3
Q

How is acidity measured?

A

Using a universal indicator with a pH scale.

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4
Q

What are soluble hydroxides?

A

Alkali

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5
Q

What are metal oxides and hydroxides?

A

Bases

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6
Q

What pH is pure water?

A

7 ie. neutral

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7
Q

What colour does universal indicator turn for acidic substances?

A

Red

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8
Q

What colour does universal indicator turn for alkali substances?

A

Purple

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9
Q

What is produced when an acid and metal react?

A

A salt and hydrogen gas

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10
Q

What is produced when an acid reacts with a base?

A

A salt and water

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11
Q

What type of reaction occurs between acids and bases?

A

Neutralisation

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12
Q

What is the equation of neutralisation in terms of ions?

A

H+(aq) + OH-(aq) —-> H2O(l)

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13
Q

What is a precipitation reaction?

A

Combining two solutions that contain different soluble salts which react to make an insoluble salt.

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14
Q

How are precipitate reactions used in water treatment?

A

Raising the pH makes insoluble metal hydroxides precipitate out.

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15
Q

What is electrolysis?

A

Breaking down a substance using electricity.

16
Q

What types of substances can be electrolysed?

A

Ionic compounds can be electrolysed when they are molten or in solution.

17
Q

What is made from electrolysis?

A

Positive ions move to the cathode while negative ions move to the anode.

18
Q

What is the electrolyte?

A

The substance being broken down.

19
Q

What are electrodes made of?

A

Inert substances such as graphite or platinum.

20
Q

Why are electrodes made of un reactive materials?

A

So the electrodes don’t react with the electrolyte or the products of electrolysis.

21
Q

What happens to the ions in electrolysis?

A

Negative ions are oxidised.

Positive ions are reduced.

22
Q

How does water affect the products of electrolysis?

A
  • The less reactive element between hydrogen and the metal is produced at the cathode.
  • At the anode, oxygen is often produced from the discharged hydroxide ions.
23
Q

What is reduction?

A

Gaining electrons

24
Q

What is oxidation?

A

Losing electrons

25
Q

How is aluminium obtained from aluminium oxide?

A

Aluminium oxide is electrolysed.

26
Q

Why is cryolite used in aluminium extraction?

A

Aluminium oxide is mixed with cryolite to lower its melting point.

27
Q

What forms at the cathode during aluminium extraction?

A

Molten aluminium.

28
Q

What is formed at the anode during aluminium extraction?

A

Oxygen which reacts with the carbon electrodes making carbon dioxide.

29
Q

Why are the carbon electrodes replaced regularly?

A

The carbon reacts with oxygen so burns away very quickly.

30
Q

What is produced when brine is electrolysed?

A

Chlorine gas, hydrogen gas and sodium hydroxide solution.

31
Q

How is chlorine from electrolysis used?

A
  • Make bleach

- Make plastics

32
Q

How is the hydrogen from electrolysis used?

A

Make margarine

33
Q

How is the sodium hydroxide from electrolysis used?

A

Make bleach, paper, soap

34
Q

What are the half equations for the electrolysis of brine?

A

2Cl-(aq) —-> Cl2(g) + 2e-

2H+(aq) + 2e- —-> H2(g)

35
Q

Give three reasons objects are electroplated.

A
  • Improve their appearance
  • Protect their surface
  • Use smaller amounts of precious metals
36
Q

How does electroplating work?

A

The object is made the cathode. The plating metal is the anode. The electrolyte contains ions of the plating metal.

GCSE Chemistry (19 decks)

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