Thermodynamics and Gibbs Flashcards
What are Joules?
Joules are a measure of energy used to quantify heat. It is measured in N*m ore = 1 kg*m^2/s^2
1 Cal = how many calories?
1 kcal or 1000 calories
What is the definition of a calorie?
The amount of energy required to raise the temperature of 1 gram of water by 1 degree celcius
What equation do we use to calculate heat?
Q=mcdeltaT m= mass of water c=specific heat capacity delta T= temp change
What is specific heat capacity (c)?
the amount of energy required to raise the tempurature of 1 gram of a substance by 1 degree celcius.
What is the specific heat capacity of water?
4.186 J/gdegreeC or 1 cal/gdegree celcius
Enthalpy
Total heat in a system H=U+PdeltaV where U= internal energy of the system H= enthalpy P=Pressure V=Volume So heat of the system is equal to the internal eneryg plus the work required to maintain it Q=deltaH
Is H - or + in endothermy?
+
Is H - or + in exothermy?
-
What are standard conditions?
1 atm and 25*C. Most enthalpy rxns will be conducted at this temp
What is the standard enthalpy of any element in its elemental state? (eg O2 is a gas)
deltaHformation=0
What is the standard enthalpy of formation?
Enthalpy of change associated with forming one mole of a compound from its elements under standard conditions
How do you calculate the enthalpy of a reaction?
deltaH rxn= deltH products= deltH reactants
What is the unit for enthalpy? What about change in enthalpy?
Enthlapy= joules, change in enthalpy=joules per mole
Bond Dissociation Energy
Enthalpy change associated with breaking bonds dlet H rxn= delt H bonds broken-delt H bonds formed
Is bond breakage endo or exothermic?
endo
Is bond formation endo or exothermic?
Exo
Hess’s Law
The total change in enthalpy is just the sum of the individual steps it took
What are the two ways to calculate enthalpy of reactions you will see on the MCAT?
Products- Reactants or Bonds Broken- Bonds formed
Gibbs free energy
Energy that can be used to perform work in a reversible reaction
What will the gibbs free energy be of a spontaneous reaction?
Negative. A spontaneous reaction is one where the products are lower in energy than the products so we see a negative change in gibbs free energy
What is the equation for gibbs free energy?
See picture:
What are the 4 major equations to know for gibbs free energy?
deltG=H-TS and deltGrxn=Gproducts-Greactants and delta G naught prime=-RTlnK, and deltG=deltGprim + RTlnQ
What is the difference between delta G and delta G naught prime?
Delta G is not in standard conditions, delta G naught prime is at 25C 1 atm and 1M