Chemistry 3.2 - Keywords Flashcards
What is meant by enthalpy?
The thermal energy stored is a chemical system
What is meant by an endothermic reaction?
Reactions when energy is taken IN from its surroundings (gets colder)
What is meant by an exothermic reaction?
Reactions when heat is given OUT to their surroundings (get hotter)
Define activation energy
The minimum amount of energy required for a reaction to take place
Define bond energy
The specific amount of energy that is needed to break a covalent bond
What is meant by average bond enthalpy?
Breaking of 1 mol of bonds
What is meant by enthalpy change?
Heat energy transferred in a reaction of constant pressure
What are the three main types of enthalpy change?
- Enthalpy change of neutralisation
- Enthalpy change of formation
- Enthalpy change of combustion
Define enthalpy change of neutralisation
The enthalpy change when one mole of water is formed from a neutralisation reaction
Define enthalpy change of formation
The enthalpy change when one mole of compound is formed from its elements in their standard state
Define enthalpy change of combustion
The enthalpy change when one mole of substance(what is being burnt) reacts completely with oxygen
What does Hess’s Law state?
The enthalpy change for a chemical reaction is independent of the route taken
( It doesn’t matter which way you go, the enthalpy change will STILL be the same
What is meant by the collision theory?
For a reaction to occur particles have to collide. They must collide with enough energy and with correct orientation
What is meant by a homogeneous catalyst?
This has the catalyst in the same phase as the reactants. Typically everything will be present as a gas or contained in a single liquid phase
