Enthalpy definitions

Question 1

standard enthalpy change of reaction

Answer 1

the enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions and standard states

Question 2

standard enthalpy change of formation

Answer 2

the enthalpy change that accompanies the formation of one mole of a compound from its elements under standard conditions and standard states

Question 3

standard enthalpy change of combustion

Answer 3

the enthalpy change that occurs when one mole of a substance reacts completely with oxygen under standard conditions in standard states

Question 4

enthalpy change of neutralisation

Answer 4

the enthalpy change that accompanies the reaction of an acid and a base to form one mole of water under standard conditions in standard states.

Question 5

average bond enthalpy

Answer 5

the energy required to break 1 mole of bonds in gaseous molecules

Question 6

activation energy

Answer 6

the minimum energy required for a reaction to take place. the energy input required to break bonds

Question 7

the role of a catalyst

Answer 7

Increase rate of reaction without being used up. To provide an alternate reaction route with lower activation energy

Question 8

homogenous catalyst

Answer 8

same state as reactants
eg. ozone depletion/ esterification

Question 9

heterogenous catalyst

Answer 9

different state to reactants
eg. alkene hydrogenation

Question 10

dynamic equilibrium

Answer 10

rate of forward reaction is equal to the rate of the backwards reaction, concentrations of products and reactants remain constant

must be in a closed system