Module 3 Enthalpy changes Flashcards
What does system mean in a chemical reaction?
The atoms and bonds involved in the chemical reaction.
What is the law of conservation?
The amount of energy in an isolated system remains the same. Energy cannot be destroyed or created, it can only be transferred from one form to another.
What energy change is breaking bonds associated with?
Energy is taken in to break bonds -> endothermic reaction.
What energy change is making bonds associated with?
Energy is released to make binds -> exothermic reaction.
What is an endothermic reaction?
A reaction with an overall positive enthalpy change -> enthalpy of products > enthalpy of reactants.
What is an exothermic reaction?
A reaction with an overall negative enthalpy change -> enthalpy of products < enthalpy of reactants.
What does activation energy mean?
The minimum energy required for a reaction to take place.
What are the standard conditions?
100kPa and 298K
Define enthalpy change of combustion.
The energy change that takes place when 1 mole of a substance is completely combusted.
Define enthalpy change of neutralisation.
The energy change that takes place when 1 mole of water is formed from a neutralisation reaction.
What does enthalpy change of reaction mean?
The energy chnage associated with a given reaction.
How can you calculate enthalpy change from experimental data?
Using the equation Q=mc x change in temp. M is the mass and C is the specific heat capacity.
What are the advantages of using a bomb calorimeter?
- Minimises heart loss
- Pure oxygen used -> ensures complete combustion
Why might experimental methods for enthalpy determination not be accurate?
Heat is lost to the suroundings, not in standard conditions and reaction may not go to completion.
What does average bond enthalpy mean?
The mean energy required to break 1 mole of bonds in gaseous molecules.
