Physical chemistry Flashcards
Enthalpy
the thermal energy stored in a chemical system
law of conservation of energy
energy cannot be created or destroyed only moved from one place to another.
ΔH=
ΔHprod-ΔHreact
exothermic reaction
- enthalpy of product is smaller than reactants
- heat loss to the surroundings
- ΔH is negative
Endothermic reactions
- enthalpy of product is greater than reactants
- heat gain to system from the surroundings
- ΔH is positive
activation energy
the minimum energy required to start a reaction by breaking bonds in the reactants.
standard conditions
298K and 100kPa
enthalpy change of formation
the energy change that takes place when one mole of a compound is formed from its constituent elements
enthalpy change of combustion
energy change that takes place when one mole of a substance is completely combusted
enthalpy change of neutralsiation
the energy change where 1 mole of water is formed from a neutralisation reaction
q=
mcΔT
specific heat capacity
energy required to raise the temperature of a 1kg substance by 1k.
Average bond enthalpy
the average energy that is required for one mole of a gaseous bond to undergo homolytic fission
hess’s law
enthalpy change in a chemical reaction is independent to the route it takes
which way do arrows point in a Hess cycle when given combustion data?
Down
