3.2.1 - Enthalpy Changes -

a) What energy change is making bonds associated with?

• Energy is released to make bonds - exothermic bonds

What energy change is breaking bonds associated with?

Energy is taken in to break bonds - endothermic reaction

b-c) Draw enthalpy diagram?

di) What are the standard conditions?

298K

100 kPa

What is activation energy?

The minimum energy required for a reaction take place

di) Define enthalpy change of reaction?

The energy change associated with given reaction

dii) Define enthalpy change of formation?

The energy change that takes place when 1 mole of a compound is formed for its reactants under state conditions 

diii) Define enthalpy change of combustion?

The energy change that takes place when 1 mole of a substance is completely combusted

dv) Define enthalpy change of neutralisation?

The energy change that takes place when 1 mole of water is formed from a neutralisation reaction

e) How can you calculate enthalpy change from experimental data?

Q= mcT

Q = energy 

M = mass

C = Specific hear capacity = 4.18gJ-1K-1

T = temperature 

What are the advantages of using a calorimeter?

• Minimises heat loss

• Pure oxygen used → ensures combustion

Why might experimental methods for enthalpy determination may not be accurate?

• Heat is lost to the surroundings

• Not in standard conditions

• Reaction may not go into completion

How to calculate enthalpy change of reaction using energy bonds?

Bond energy reactants - Bond energy of products