Chemical Changes

Question 1

What is the formula for hydrochloric acid?

Answer 1

HCl

Question 2

What is the formula for nitric acid?

Answer 2

HNO₃

Question 3

What is the formula for sulfuric acid?

Answer 3

H₂SO₄

Question 4

What makes an acid strong?

Answer 4

Fully ionising in a solution.

Question 5

What is the main laboratory base?

Answer 5

Sodium hydroxide

Question 6

What does caustic mean?

Answer 6

Can burn skin and damage materials

Question 7

What are alkalis

Answer 7

Soluable bases

Question 8

What is the general equation for neutralisation?

Answer 8

Acid + base ➝ salt and water

Question 9

What does pH mesure?

Answer 9

The number of H⁺ ions in a solution

Question 10

How much does the concentration of H⁺ ions need to be reduced to change pH by 1 unit?

Answer 10

Decreased by a factor of 10.

Question 11

What is oxidation

Answer 11

• Gaining oxygen
• Loosing electrons

Question 12

What is reduction?

Answer 12

• Loosing oxygen
• Gaining electrons

Question 13

What is a displacement reaction?

Answer 13

Where a more reactive element takes the place of a less reactive one in a compound.

Question 14

What is an ore?

Answer 14

A rock with enough metal compound in it to make it worth extracting

Question 15

How can metals less reactive than carbon be extracted from their ores?

Answer 15

Reduction with carbon.
This forms the metal and carbon dioxide.

Question 16

Acid + base ➝ ______ + ______

Answer 16

salt + water

Question 17

Acid + metal ➝ ______ + ______

Answer 17

salt + hydrogen

Question 18

Acid + metal oxide ➝ ______ + ______

Answer 18

salt + water

Question 19

Acid + metal carbonate ➝ ______ + ______ + _____

Answer 19

salt + water + carbon dioxide

Question 20

What chemicals can be separated using electrolysis?

Answer 20

Ionic compounds

Question 21

What is the cathode?

Answer 21

The negative electrode

Question 22

What is the anode?

Answer 22

The positive electrode

Question 23

What is a cation?

Answer 23

A positive ion which moves to the cathode.

Question 24

What is an anion?

Answer 24

A negative ion which move to the anode.

Question 25

What is the electrolyte?

Answer 25

An ionic substance, which is ether molten or in a solution.

Question 26

What is aluminium ore called?

Answer 26

Bauxite.

Question 27

What is the chemical formula for aluminium ore?

Answer 27

Al₂O₃

Question 28

What is put into the solution with aluminium ore for electrolysis, and why?

Answer 28

**Molten cryolite.** This reduces the melting point to save energy and money.

Question 29

What is cryolite?

Answer 29

An aluminium based compound.

Question 30

Why do the anodes need to be replaced regularly in the extraction of aluminium ore?

Answer 30

They are made from graphite, so the oxygen produced reacts with the carbon in the anodes.

Question 31

What is the rule for the products at the **cathode** for aqueous solutions?

Answer 31

Hydrogen is produced unless the metal is less reactive than hydrogen.

Question 32

What is the rule for the products at the **anode** for aqueous solutions?

Answer 32

Oxygen is formed unless there is a halide ion.

Question 33

Is the reaction between the electrodes and electrolyte in a cell exothermic or endothermic?

Answer 33

Exothermic.

Question 34

How does the types of metals effect the voltage generated in a cell?

Answer 34

The bigger the difference in their reactivity the greater the voltage produced.

Question 35

What happen if the same metal is used for both electrodes in a chemical cell?

Answer 35

0 volts are produced, as their reactivity is the same.

Question 36

What 3 factors effect the voltage generated by a battery?

Answer 36

- Type of metals used - Type of electrolyte - How many cells are joined together

Question 37

What is a battery?

Answer 37

Many cells joined together.

Question 38

How are batterys recharged?

Answer 38

Recharging a battery reverses the reaction so it can be used again.

Question 39

What is a fuel cell?

Answer 39

An electrical cell which uses fuel (hydrogen) and oxygen to release energy in a reaction which is transferred to electrical energy.

Question 40

How is hydrogen stored?

Answer 40

In pressurised containers.