chemical_changes

Question 1

Oxidation

Answer 1

When a substance gains oxygen

Question 2

Reduction

Answer 2

When a substance loses oxygen

Question 3

Reactivity series of metals

Answer 3

The series shows the metals in order of their reactivity.

Question 4

Reactivity with acids

Answer 4

Metals above H2 in reactivity series react with acid to produce H2.

Question 5

Reactivity trends

Answer 5

The more reactive the metal is

Question 6

Metals below H2

Answer 6

Metals below H2 don’t react with acids.

Question 7

Unreactive metals in Earth

Answer 7

In their natural state (well

Question 8

Extraction of metals less reactive than carbon

Answer 8

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

Question 9

Extraction of metals more reactive than carbon

Answer 9

By electrolysis

Question 10

Oxidation in terms of electron transfer

Answer 10

Loss of electrons

Question 11

Reduction in terms of electron transfer

Answer 11

Gain of electrons

Question 12

General equation for reaction between metals and acids

Answer 12

Metal + acid → salt + hydrogen

Question 13

Type of reaction between metals and acids

Answer 13

Redox reaction

Question 14

Metals that react with acid

Answer 14

Those above hydrogen

Question 15

General equation for a neutralisation reaction

Answer 15

Base + acid → salt + water

Question 16

General equation for reaction between metal carbonate and acid

Answer 16

Metal carbonate + acid → salt + water + carbon dioxide

Question 17

General equation for reaction between metal oxides and acids

Answer 17

Metal oxide + acid → a salt + water

Question 18

Redox reaction

Answer 18

A reaction that involves both oxidation and reduction.

Question 19

Redox Reaction

Answer 19

A reaction where both oxidation and reduction occurs.

Question 20

Oxidation of Magnesium

Answer 20

Magnesium has lost electrons and thus has been oxidised (Mg to Mg2+).

Question 21

Reduction of Hydrogen

Answer 21

The hydrogen in HCl has gained electrons and thus has been reduced (H+ to H2).

Question 22

Formation of Soluble Salt

Answer 22

React the excess acid with some insoluble chemical (e.g. metal oxide)

Question 23

Products of Acids and Alkalis

Answer 23

Acids produce hydrogen ions

Question 24

Definition of Bases

Answer 24

Acids

Question 25

pH Scale

Answer 25

The measure of acidity/alkalinity of a solution; neutral solution.

Question 26

Neutralisation Reaction Equation

Answer 26

H+ + OH− → H2O.

Question 27

Strong Acid

Answer 27

Strong acid is completely ionised in aqueous solution.

Question 28

Weak Acid

Answer 28

Weak acid is only partially ionised in aqueous solution.

Question 29

Effect of H+ Concentration on pH

Answer 29

The pH decreases as the concentration of H+ increases.

Question 30

Concentrated Acid

Answer 30

Concentrated acid has more moles of acid per unit volume than dilute.

Question 31

Dilute Acid

Answer 31

Dilute refers to solutions of low concentrations.

Question 32

Strength vs Concentration of Acids

Answer 32

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 33

Change in H+ Concentration with pH

Answer 33

As the pH is decreased by one unit

Question 34

LiNO3

Answer 34

Lithium nitrate

Question 35

K2CO3

Answer 35

Potassium carbonate

Question 36

MgBr2

Answer 36

Magnesium bromide

Question 37

BaSO4

Answer 37

Barium sulfate

Question 38

Electrolysis

Answer 38

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 39

Electrolyte

Answer 39

The liquid/solution which conducts electricity.

Question 40

Cathode

Answer 40

The negative electrode.

Question 41

Anode

Answer 41

The positive electrode.

Question 42

Reduction at the Cathode

Answer 42

Reduction occurs at the cathode.

Question 43

Oxidation at the Anode

Answer 43

Oxidation occurs at the anode.

Question 44

Discharged Element at Cathode

Answer 44

The less reactive element discharges at the cathode. Hydrogen is produced unless there is a less reactive metal

Question 45

Oxygen Production at Anode

Answer 45

Oxygen is produced at the anode unless the solution contains halide ions

Question 46

Aluminium Manufacturing

Answer 46

Aluminium is made through the electrolysis of aluminium oxide and cryolite.

Question 47

Cost of Aluminium Production

Answer 47

Lots of energy is needed to produce the current in electrolysis which makes this process expensive.

Question 48

Half Equations in Aluminium Extraction

Answer 48

Al3+ + 3 e− → Al (cathode); 2 O2− → O2 + 4 e− (anode). Oxygen reacts with C of the anode producing CO2.

Question 49

Cryolite Usage

Answer 49

It lowers the melting point of aluminium oxide

Question 50

Half Equations in Electrolysis of Aqueous Na2SO4

Answer 50

2 H+ + 2 e− → H2 (cathode); 4 OH− → 2 H2O + O2 + 4 e− (anode).

Question 51

Half Equations in Electrolysis of Molten and Aqueous KCl

Answer 51

K+ + e− → K (cathode); 2 Cl− → Cl2 + 2 e− (anode). 2 H+ + 2 e− → H2 (cathode); 2 Cl− → Cl2 + 2 e− (anode)

Question 52

Half Equations in Electrolysis of Aqueous CuBr2

Answer 52

Cu2+ + 2 e− → Cu (cathode); 2 Br− → Br2 + 2 e− (anode).