CHM8 - Enthalpy & Thermochemistry Flashcards
Calculation for enthalpy change
ΔH = H(final) - H(Initial)
H(Final) represents the enthalpy of the reaction products
H(initial) represents the enthalpy of the reaction reactants
What would a positive (+ΔH) indicate?
An endothermic reaction
What is the Standard Heat of formation/Enthalpy of formation (Δ\/fH⊖)?
The change of enthalpy that would occur when one mole of a substance is formed from it;s constituent elements in a standard state reaction. (KJ/mol)
What is Hess’s law?
ΔH(Overall) = ΔH1 + ΔH2
For two reactions in sequence
What is the enthalpy formation?
The enthalpy change that acompanies the formation of a compound.
What is bond dissociation energy?
Measure of the strength of a bond
Formula to calculate the heat required to change a substance from one temperature to another.
Q = mC(T2-T1)
Where:
m=No. Moles
C= Specific heat capacity
Second law of thermodynamics
Entropy of an isolated system will never decrease
What is Entropy?
The level of disorder in a system
What value of Gibbs free energy is considered to be spontaneous?
if ΔG<0 and vice versa
Whenever ‘Rate’ is used, it refers to the…
Overall rate of a reaction
What are the three elementary steps of the reaction mechanism?
Initiation - Reactant molecules become free radicals
Propagation - Reaction between radicals
Termination - New molecule is formed
What is activation energy E\/a?
The energy required to start a reaction
What is the period before reactants transform into the final products?
The Activated complex
How to catalysts affect a reaction?
They lower the activation energy
What is saturation kinetics?
When all the active sites on an enzyme are in use and the reaction rate no longer increases
What is Le Chatelier’s principle?
Whenever a perturbation is applied to a system at equillibrium, the system evolves in such a way as to compensate for the applied perturbation.
