Definitions Flashcards
Hess’s Law
The enthalpy change for a chemical reaction is the same regardless of the route taken from reactant to products
Enthalpy of formation
The enthalpy change when one mole of compounds is formed from its constituent elements, under standard conditions, all reactants and products in their standard states
Enthalpy of combustion
The enthalpy change when one mole of compound is completely burnt in oxygen under standard conditions, all reactants and products in their standard state
Standard enthalpy of atomisation
The enthalpy change when one mole of gaseous atoms is formed from an element in its standard state
Mean bond enthalpy
The energy required to break one mole of covalent bonds into gaseous atoms, averaged over a range of different compounds
Explain how a catalyst increases the rate of reaction
Lowers the activation energy
Provides an alternative route
Catalyst
A substamce that speeds up the rate of reaction but remains chemically unchanged at the end
How does a catalyst work
Provides an alternative route
Lowers the activation energy
Effect of a catalyst on the time taken to reach EQ
Decreases/shorter
Effect of a catalyst on the position of EQ
None
Activation energy
The minimum amount of energy required for a reaction to occur/to go/start
Or for successful collisions
Le Chatelier’s principle
The position of the EQ will shift to appose any change made to it
Enthalpy change
Heat change at a constant pressure
First ionisation energy
The standard enthalpy change when one mole of electron is removed from one mole of gaseous atoms to give one mole of gaseous ions each with a single positive charge
Second ionisation energy
The standard enthalpy change when one mole of electrons is removed from one mole of gaseous 1+ ions to give one mole of gaseous ions each with a 2+ charge
