C2 - Salts & Electrolysis Flashcards Preview

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Flashcards in C2 - Salts & Electrolysis Deck (37)
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What are acids?

Substances that produce H+ ions when added to water.

1

What is an alkali?

-A soluble hydroxide.
-Produce OH- ions when added to water.

2

What are bases?

Substances which neutralise acids.

3

How is acidity measured?

Using a universal indicator with a pH scale.

4

What are soluble hydroxides?

Alkali

5

What are metal oxides and hydroxides?

Bases

6

What pH is pure water?

7 ie. neutral

7

What colour does universal indicator turn for acidic substances?

Red

8

What colour does universal indicator turn for alkali substances?

Purple

9

What is produced when an acid and metal react?

A salt and hydrogen gas

10

What is produced when an acid reacts with a base?

A salt and water

11

What type of reaction occurs between acids and bases?

Neutralisation

12

What is the equation of neutralisation in terms of ions?

H+(aq) + OH-(aq) ----> H2O(l)

13

What is a precipitation reaction?

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

14

How are precipitate reactions used in water treatment?

Raising the pH makes insoluble metal hydroxides precipitate out.

15

What is electrolysis?

Breaking down a substance using electricity.

16

What types of substances can be electrolysed?

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

17

What is made from electrolysis?

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

18

What is the electrolyte?

The substance being broken down.

19

What are electrodes made of?

Inert substances such as graphite or platinum.

20

Why are electrodes made of un reactive materials?

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

21

What happens to the ions in electrolysis?

Negative ions are oxidised.
Positive ions are reduced.

22

How does water affect the products of electrolysis?

-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

What is reduction?

Gaining electrons

24

What is oxidation?

Losing electrons

25

How is aluminium obtained from aluminium oxide?

Aluminium oxide is electrolysed.

26

Why is cryolite used in aluminium extraction?

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

27

What forms at the cathode during aluminium extraction?

Molten aluminium.

28

What is formed at the anode during aluminium extraction?

Oxygen which reacts with the carbon electrodes making carbon dioxide.

29

Why are the carbon electrodes replaced regularly?

The carbon reacts with oxygen so burns away very quickly.