Thermodynamics Flashcards
(18 cards)
What is Hess‘s Law?
The enthalpy change of a chemical reaction is independent of the path it takes. This means we can find ΔrH for any question
What is Standard Enthalpy of formation?
The enthalpy change for the formation of 1 mol of a compound from its elements in their standard state products - reactants
What is standard enthalpy of combustion?
Burning 1 mol of a compound in oxygen under standard conditions
What is Calaimetry?
Enthalpy change in a reaction can be related to the heat absorbed or produced from a known amount of reactants
What is specific heat capacity?
The amount of heat needed to raise the temperature of 1g of substance to 1•C
What is Enthalpy?
Measure of total heat content of a system at constant pressure. H=U+PV. Where U is internal energy, P is pressure V is volume. Enthalpy comes from internal energy of the system and the energy required to make room for it by displacing its environment (PV work)
What is internal energy?
U. Comes from microscopic components of a system- kinetic and potential energy of the atoms and molecules
What is the first law of thermodynamics?
Energy cannot be created or destroyed, only transferred or converted ΔU =q+w (w is work)
What are intensive properties?
An intensive property Does not depend on the amount of substance eg temperature
What is extensive property?
An extensive property does depend on the amount of substance eg mass
What is the second law of thermodynamics?
In any natural thermodynamic process, the total entropy of a isolated system can never decrease over time. It either increases or remains constant. Entropy increases in closed system.
What is entropy?
The dispersal of energy throughout a system and its surroundings. Increased entropy means increased degrees of freedom for molecules within the system. I.e molecules can do more stuff
What is the calculation for calorimetry?
Q=Cs x m x ΔT and ΔT = Tfinal - Tinitial
What is calculation for enthalpy change?
ΔrH = -q/n and stoichiometry n=m\M
What is the standard enthalpy of formation calculation?
ΔfH = sum of ΔfH products - sum of ΔfH reactants
What is calculation for bond energy?
ΔrH = sum of bonds broken - sum of bonds made
What is ΔSuniverse?
ΔS universe = Δ S surroundings + Δ S system
What is gibbs free calculation? With rearranging?
ΔG = ΔH-TΔS for gibbs, T = ΔH-ΔG / ΔS for temperature, ΔH = ΔG+TΔS for enthalpy change, ΔS = ΔH-ΔG/T for entropy
