Topic 4

Question 1

What is oxidation/reduction ?

Answer 1

Oxidation- when a substance gains oxygen
Reduction - when a substance loses oxygen

Question 2

What is the reactivity series of metals ?

Answer 2

The series shows the metals in order of their reactivit

Question 3

What is a displacement reaction ?

Answer 3

A reaction where a more reactive metal displaces a less reactive metal from a compound

Question 4

How are unreactive metals found in earth?

Answer 4

In their natural state

Question 5

How can metals less reactive than carbon be extracted ?

Answer 5

Reduction with carbon. Carbon displaces the metal in metal oxide - gets oxidised to carbon oxides . Metal from the metal oxide gets reduced to the pure metal

Question 6

How are metals more reactive than carbon extracted ?

Answer 6

By electrolysis

Question 7

How are oxidation and reductiom defined in terms of electron transfer ?

Answer 7

Oxidation - loss of electrons
Reduction - gains of electrons

OILRIG

Question 8

What is the general equation for a reaction between metals and acids ? What type of reaction is this ?

Answer 8

Metal + acid –> salt + hydrogen

Redox reaction, also a displacement reaction

Question 9

Which metals in the reactivity series will react with acid ?

Answer 9

Those above hydrogen

Question 10

What is the general equation for a neutralisation reaction ?

Answer 10

Base + acid —> salt + water

Question 11

What is the general equation for the reaction between metal carbonate and acid ?

Answer 11

Metal carbonate + acid —> salt + water + carbon dioxide

Question 12

What is the general equation for the reaction between metal oxides and acids ?

Answer 12

Metal pxide + acid —> a salt + water

Question 13

What is a redox reaction ?

Answer 13

A reaction where both oxidation and reduction occurs

Question 14

How is a soluble salt formed ?

Answer 14

a) react the excess acid with some insolible chemical (e.g. metal oxide)
b) filter off the leftovers
c) crystallise the product

Question 15

What do acids and alkalis produce in aqueous solutions?

Answer 15

Acids produce hydrogen ions , alkalis produce hydroxide ions

Question 16

What are bases , acids and alkalis ?

Answer 16

Bases are compounds that neutralise acids , acids produce hydrogen ions in aqueous solutions , alkalis are soluble bases - produce hydroxide ions in aqueous solutions

Question 17

What is the pH scale and what does a pH of 7 show ?

Answer 17

The measure of acidity/alklainity of a solution; neutral solution

Question 18

What is a strong acid ? What is a weak acid ?

Answer 18

Strong acid is completely ionised in aqueous solution; what acid is only partially ionised in aqueous solution

Question 19

What is a concentrated acid and what is a dilute acid ? Is this the same as a strong and weak acid ?

Answer 19

• Concentrated acid has more moles of acid per unit volume than dilute (dilute refers to solutions of low concentrations)
• It is not the same - concentration is not the same thing as strength of an acid.
• Strength refers to whether the acid is completely ionised in water (strong) or only partially (weak).

Question 20

What is electrolysis ?

Answer 20

The passing of an electric current through ionic substances that are molten or in solution to break them down into elements; ions are discharged (they lose/gain electrons) at electrodes to produce these

Question 21

What is an electrolyte ?

Answer 21

The liquid/solution which conducts electricity

Question 22

What is a cathode and what is an anode ?

Answer 22

Cathode is the negative electrode , anode is the positive electrode

Question 23

What occurs at the cathode and what occurs at the anode during electrolysis ?

Answer 23

Reduction occurs at the cathode
Oxidation occurs at the anode

Question 24

In aqueous electrolysis , which element is discharged at the cathode ? Oxygen is produced at the anode unless what ?

Answer 24

The less reactive element discharges at the cathode. Hydrogen is produced unless there is a less reactive metal, in which case the said metal is produced. Oxygen is produced at the anode unless the solution contains halide ions, in which case halogen molecules are produced

Question 25

How is aluminium manufactured ? Why is it expensive ?

Answer 25

Aluminium is made through the electrolysis of aluminium oxide and cryolite.
Lots of energy is needed to produce the current in electrolysis which makes this process expensive.