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
