Chemical changes

Question 1

What does the pH scale measure?

Answer 1

How acidic or alkali something is

Question 2

What is the pH of an acid

Answer 2

0-6

Question 3

What is the pH of an alkali?

Answer 3

8-14

Question 4

What does an acid form in water?

Answer 4

H+ ions

Question 5

What does an alkali produce in water?

Answer 5

OH- ions

Question 6

What is the name of the reaction between an acid and a base?

Answer 6

Neutralisation

Question 7

Why is the pH different in strong and weak acids?

Answer 7

Strong acids have more H+ ions

Question 8

What does oxidation and reduction mean?

Answer 8

Oxidisation - a gain in oxygen or loss of electrons
Reduction - a loss in oxygen or gain of electrons

Question 9

What is a redox reaction?

Answer 9

A reaction where reduction and oxidisation is happening simultaneously

Question 10

What is a displacement reaction?

Answer 10

A more reactive metal will displace a less reactive metal from its compound. They are redox reactions

Question 11

Give a word and symbol equation as an example of a displacement reaction

Answer 11

Iron + copper sulphate -> copper + iron sulphate
Fe + CuSo4 -> FeSo4 + Cu

Question 12

What is an ionic equation?

Answer 12

An ionic equation is an equation where only the particles that react and the products are shown.

Question 13

What is electrolysis?

Answer 13

The process of splitting up an ionic compound with electricity

Question 14

What substances can be electrolysed?

Answer 14

Electrolysis works with both molten ionic solids and aqueous solutions

Question 15

When electrolysing molten solids, what forms at the anode?

Answer 15

Non metal ions are oxidised (lose electrons)

Question 16

When electrolysing molten solids, what forms at the cathode?

Answer 16

Positive metal ions - they are reduced - gain electrons

Question 17

Which way do ions move in electrolysis?

Answer 17

Positive ions move towards the cathode and gain electrons.
Negative ions move toward the anode and lose electrons

Question 18

What electrode is negative and what one is positive?

Answer 18

The cathode is negative and the anode in positive

Question 19

When electrolysing aqueous solutions, what forms on the cathode?

Answer 19

If H+ ions and metal ions are present, hydrogen gas will be produced if the metal ions form a metal more reactive than hydrogen. If the metal is less reactive than hydrogen the metal will be produced instead

Question 20

When electrolysing aqueous solutions, what forms around the anode?

Answer 20

If OH- ions and halide ions are present the halide will be produced, if no halide is present then OH- ions are discharged and oxygen is formed.

Question 21

What are half equations?

Answer 21

Half equations are used to show the reactions at both electrodes. Half equations need balanced electrons on both the negative and positive equation.

Question 22

What is the point of a titration?

Answer 22

A titration is used to find out exactly how much acid is needed to neutralise a quantity of alkali

Question 23

What indicator is most commonly used for titration?

Answer 23

Phenolphthalein

Question 24

What colours is phenolphthalein when acid and alkali?

Answer 24

Acid - clear
Alkali - pink

Question 25

What colours is litmus when acid and alkali?

Answer 25

Acid - red
Alkali - blue/purple

Question 26

What colour is methyl orange when acid or alkali?

Answer 26

Acid - red
Alkali - yellow

Question 27

What is the order of the reactivity series?

Answer 27

Potassium, sodium, lithium, calcium, magnesium, carbon, zinc, iron, hydrogen, copper

Question 28

What are the two ways of extracting metals from metal oxides?

Answer 28

More reactive than carbon - electrolysis
Less reactive than carbon - reduction my carbon

Question 29

What are some metals more reactive than others?

Answer 29

It depends on the metals tendency to form positive ions