Topic 4 - Chemical Changes

Question 1

What are metal oxides?

Answer 1

Metals reacted with oxygen

Question 2

What are oxidation reactions?

Answer 2

When the reactant gains oxygen

Question 3

What happens when metals react with other substances?

Answer 3

The metal atoms form positive ions

Question 4

What is the reactivity of a metal related to?

Answer 4

It’s tendency to form positive ions

Question 5

What is the reactivity series?

Answer 5

Lists metals in order of their reactivity towards other substances

Question 6

What is the reactivity series?

Answer 6

Potassium 
Sodium 
Lithium 
Calcium 
Magnesium 
Carbon 
Zinc 
Iron 
Hydrogen 
Copper

Question 7

What is the equation for a metal reacting with an acid?

Answer 7

Acid + metal -> salt + hydrogen

Question 8

Describe how a metal reacts with an acid

Answer 8

Speed of reaction = rate at which hydrogen bubbles are given off

Question 9

What is the equation for a metal reacting with water?

Answer 9

Metal + water -> metal hydroxide + hydrogen

Question 10

Where are un reactive metals found? Give an example.

Answer 10

Gold found in earth as metal itself

Question 11

How are most metals found?

Answer 11

As compounds that require chemical reactions to extract the metal

Question 12

How can metals less reactive than carbon be extracted form their oxides?

Answer 12

Reduction with carbon

Question 13

What does reduction involve?

Answer 13

The loss of oxygen

Question 14

What is oxidation in terms of electrons?

Answer 14

Loss of electrons

Question 15

What is reduction in terms of electrons?

Answer 15

Gain of electrons

Question 16

What are redox reactions?

Answer 16

When reduction and oxidation happen at the same time

Question 17

What neutralises acids?

Answer 17

Alkalis and bases

Question 18

What is the word equation for the reaction between and acid and a base?

Answer 18

Acid + base -> salt + water

Question 19

What does the salt produced in a reaction between an acid and an alkali depend on?

Answer 19

The acid used

The positive ions in base or alkali

Question 20

How can soluble salts be made?

Answer 20

By reacting acids with solid insoluble substances such as metals, metal oxides, hydroxides or carbonates
The solid is added to the acid until no more reacts when the excess solid is filtered off

Question 21

How do you form solid salts?

Answer 21

Salt solutions can be crystallised

Question 22

What do acids produce in aqueous solutions?

Answer 22

Hydrogen ions

Question 23

What do aqueous solutions of alkalis contain?

Answer 23

Hydroxide ions

Question 24

How do you measure ph?

Answer 24

Universal indicator or ph probe

Question 25

What is the word equation for neutralisation reactions?

Answer 25

hydrogen ions + hydroxide ions -> water

Question 26

How do you measure the volumes of acid and alkali solutions that react with each other?

Answer 26

Titrations using a suitable indicator

Question 27

Give examples of a strong acid

Answer 27

Hydrochloric
Nitric
Sulphuric

Question 28

What happens to a strong acid in an aqueous solution?

Answer 28

Completely ionised

Question 29

What happens to a weak acid in an aqueous solution.

Answer 29

Partially ionised

Question 30

Give examples of weak acids

Answer 30

Ethanoic
Citric
Carbonic

Question 31

As the ph of an acid increases by one unit what happens to the concentration of the hydrogen ion?

Answer 31

Increases by a factor of 10

Question 32

What are electrolytes?

Answer 32

The liquids and solutions that are able to conduct electricity because the ions are free to move about within the solution as an ionic compound was melted or dissolved in water

Question 33

What does passing electric current through electrolytes cause the ions to do?

Answer 33

Positively charged ions move to the negative electrode (cathode)
Negatively charged ions move to the positive electrode (anode)

Question 34

What is electrolysis?

Answer 34

When ions are discharged at the electrodes producing elements

Question 35

What happens when a simple ionic compound is electrolysed in the molten state using inert electrodes?

Answer 35

The metal is produced at the catfood and the non-metal is produced at the anode

Question 36

How can metals be extracted from molten compounds?

Answer 36

Electrolysis

Question 37

When is electrolysis used to extract metals?

Answer 37

If the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon

Question 38

Why are large amounts of energy needed during the extraction process of metals by electrolysis?

Answer 38

To melt the compounds and produce electrical current

Question 39

How is aluminium manufactured?

Answer 39

By the electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the positive electrode (anode)

Question 40

What do the ions discharged when aqueous solution is electrolysed using inert electrodes depend on?

Answer 40

The relative reactivity of the elements involved

Question 41

During electrolysis of aqueous solutions when and where is hydrogen and oxygen produced?

Answer 41

Hydrogen is produced at the cathode if the metal is more reactive than hydrogen
Oxygen is produced at the anode unless the solution contains halide ions when the halogen is produced

Question 42

Why does electrolysis of aqueous solutions happen in this way?

Answer 42

Because in the aqueous solution water molecules breakdown producing hydrogen ions and hydroxide ions that are discharged

Question 43

What happens when positively charged ions gain electrons at the cathode?

Answer 43

Reactions are reductions

Question 44

What happens when negatively charged ions lose electrons at the anode?

Answer 44

Reactions are oxidations

Question 45

What are half equations?

Answer 45

They show the reactions at the electrodes to make sure the electrons balance