Chemical energetics

Question 1

what is an exothermic reaction?

Answer 1

reaction that transfers
thermal energy to the surroundings leading to an increase in the temperature of the surroundings

Question 2

What is an endothermic reaction?

Answer 2

reaction that takes in
thermal energy from the surroundings leading to a decrease in the temperature of the surroundings

Question 3

What is the transfer of thermal energy during a reaction called?

Answer 3

the enthalpy change ∆H

Question 4

is ∆H negative or positive in exothermic reactions

Answer 4

negative

Question 5

is ∆H negative or positive in endothermic reactions

Answer 5

positive

Question 6

define activation energy

Answer 6

minimum energy that colliding particles must have to react

Question 7

what is the symbol for activation energy

Answer 7

Ea

Question 8

is bond breaking an endothermic or exothermic reaction?

Answer 8

edothermic

Question 9

is bond making an edothermic or exothermic reaction?

Answer 9

exothermic

Question 10

what is an example of an exothermic reaction?

Answer 10

combustion
neutralisation

Question 11

what is an example of an edothermic reaction?

Answer 11

hand warmers
self heating cans

Question 12

How can we calculate the enthalpy change of a reaction using bond energies

Answer 12

Add together all the bond energies for all the bonds in the reactants – this is the
‘energy in’.
Add together the bond energies for all the bonds in the products – this is the
‘energy out’.
Calculate the energy change: energy in – energy out

Question 13

What does it mean if If the energy out > energy in?

Answer 13

the energy change will be negative showing an exothermic reaction

Question 14

What does it mean if the energy out<energy in?

Answer 14

will be positive showing
an endothermic reaction.

Question 15

What can Reaction profiles be used to show?

Answer 15

an be used to show the relative energes of
reactants and products, the activation energy and the overall
energy change of a reaction.