Sub Topic 2 - Enthalpy

Question 1

Endothermic changes cause heat to be

Answer 1

released to the surroundings

Question 2

Endothermic changes cause absorption of

Answer 2

heat from the surroundings

Question 3

A potential energy diagram can be used to show

Answer 3

the energy path for a reaction

Question 4

The enthalpy change is the energy difference between

Answer 4

products and reactants

Question 5

The enthalpy change can be calculated from a

Answer 5

potential energy diagram

Question 6

The enthalpy change for an exothermic reaction is

Answer 6

negative

Question 7

The enthalpy change for an endothermic reaction is

Answer 7

positive

Question 8

The activated complex is an

Answer 8

unstable arrangement of atoms

Question 9

The activated complex is formed at the

Answer 9

maximum of the potential energy barrier during a reaction.

Question 10

The activation energy is the energy required by

Answer 10

colliding molecules to form an activated complex

Question 11

The activation energy can be calculated from

Answer 11

potential energy diagrams

Question 12

A potential energy diagram can be used to show the effect of a catalyst on

Answer 12

activation energy

Question 13

An example of an exothermic reaction is

Answer 13

thermite Reaction

Question 14

During an exothermic reaction what happens to the temperature of the surroundings ?

Answer 14

It rises because heat is being given out

Question 15

In enthalpy terms ‘the surroundings’ means

Answer 15

the container, the air around about, the reactant mixture itself.

Question 16

In an exothermic reaction heat energy is

Answer 16

released to the surroundings

Question 17

In an endothermic reaction heat is

Answer 17

absorbed from the surroundings

Question 18

Bond breaking is

Answer 18

Endothermic as energy is taken in

Question 19

Bond making is

Answer 19

Exothermic (gives energy out)

Question 20

During an exothermic reaction, potential energy possessed by the reactants is

Answer 20

released to the surrounds

Question 21

The products of an exothermic reaction have _____ potential energy than the reactants

Answer 21

LESS

Question 22

The products of an endothermic reaction have ______ potential energy than the reactants

Answer 22

MORE

Question 23

The enthalpy change is the difference in energy between

Answer 23

reactants and products

Question 24

The enthalpy change has the symbol

Answer 24

∆H

Question 25

The enthalpy change can be expressed as

Answer 25

∆H = Hp - Hr

Question 26

Hp = the enthalpy of the

Answer 26

products

Question 27

Hr = the enthalpy of the

Answer 27

reactants

Question 28

This potential energy diagram is one of a ______ reaction

Answer 28

Exothermic

Question 29

This potentail energy digram is one of a _______ reaction

Answer 29

Endothermic

Question 30

Area Y is

Answer 30

∆H

Question 31

Area X is

Answer 31

Ea

Question 32

In an exothermic reaction the reactants are\_\_\_\_\_\_ than the products

Answer 32

Higher

Question 33

In an endothermic reaction the reactants are _______ lower than the products

Answer 33

lower

Question 34

For an exothermic reation the enthalpy change calculation is

Answer 34

∆H = Hp - Hr = Small number - Large number = negative

Question 35

In an endothermic reaction the enthalpy calculation is

Answer 35

∆H = Hp-Hr = Large number - small number = positive

Question 36

A catalyst decreases the

Answer 36

activation energy of a reaction

Question 37

Which line shows the exothermic reaction without a catalyst? Green or Red

Answer 37

Green

Question 38

A catalyst speeds up a reaction by ________ the activation energy

Answer 38

decreasing

Question 39

The enthalpy of combustion of a substance is the enthalpy change when

Answer 39

one mole of the substance burns completely in oxygen

Question 40

The enthalpy of solution of a substance is the energy change

Answer 40

when one mole of a substance dissolves in water. ## Footnote

Question 41

The enthalpy of neutralisation of an acid is the enthalpy change when

Answer 41

the acid is neutralised to form one mole of water

Question 42

The enthalpy changes can be calculated using the formula"

Answer 42

Eh= cm ∆T

Question 43

Enthalpy of Combustion: The energy change when

Answer 43

one mole of a substance burns completely in oxygen

Question 44

Eh = cm∆T the C represents the

Answer 44

specific heat capacity of water = 4.18 kj

Question 45

Eh = cm∆T the m represents the

Answer 45

mass of water in kg

Question 46

Eh = cm∆T the ∆T represents the

Answer 46

the temperature change in C°

Question 47

The Enthalpy of Solution: The energy change when

Answer 47

one mole of a substance dissolves compeltely in water

Question 48

The Enthalpy of Neutralisation: The Enthalpy of Neutralisation is the energy change when

Answer 48

one mole of water is formed in a neutralisation reaction.