Thermodynamics Lectures 1-11 Flashcards
What is the sign for delta, sigma and proportional to?
∆
∑
∝
What is Boyles Law?
Pressure and Volume are inversely proportional to eachother.
pV = nRT
Pressure: Pa or J/m^3
Volume: m^3
Number: mol
Temperature: K
R = 8.314 J/Kmol
Forms of energy in biochemistry:
Potential:
Bond Energy.
Chemical Energy (conc difference across gradient).
Electrical Energy (of charge seperation).
Kinetic:
Thermal Energy (of molecular motion).
Radiant Energy (of photons).
Electrical Energy (of moving charged particles).
What is the first law of thermodynamics?
Energy cannot be created or destroyed, it just exists in different forms.
Relationship between System and Surroundings?
Universe - System = Surroundings.
What is an open system?
A system in which energy and matter are exchanged.
What is a closed system?
A system where only energy is exchanged.
What is an isolated system?
A system where no exchange is taking place.
What is internal energy?
The energy within a system.
A substance which has:
-energy of bonds,
-energy of molecular movements,
-a state function.
What is the equation for change in energy?
∆E = q + w
Change in energy = heat + work.
What is work and heat?
Work is the displacement of an object.
Heat is a change in the temperature of an object.
What is the equation for work?
Work = force x distance.
Can be calculated if you run a reaction through a closed vessel fitted with a piston.
The volume of gas increases, pushing out the piston. Work done is the change in volume of gas.
w = -P∆V
Negative because energy is being transferred into the surroundings.
What is the equation for enthalpy?
H = E + PV
When a system is at constant pressure, enthalpy change depends on change in internal energy and volume.
∆H = ∆E + P∆V
Combining the equations for ∆E, w and ∆H.
∆H = q
What is positive enthalpy?
Heat is absorbed into the system.
System gains enthalpy from surroundings.
∆H(sys) > 0
What is negative enthalpy?
Heat is released by the system.
The system loses enthalpy.
∆H(sys) < 0
What is the change in enthalpy?
∆H = H(products) - H(reactants)
How can we measure ∆H?
Bomb Calorimeter.
∆H = q = ms∆T
specific heat capacity = energy needed to raise 1 kg of water by 1 degree.
For water, its 4.184 J g^-1 K^-1
What are standard conditions?
1 mol
298.15 K
1 atm
∆H0 = q = ms∆T
What is Hess’s Law?
∆H0 = ∑n∆Hf0(products) - ∑m∆Hf0(reactants)
∆Hf0 is enthalpy of formation.
Is negative if reaction is exothermic.
What is the enthalpy of formation?
The amount of enthalpy involved in generating 1 molecule of it from its elements.
Forward and reverse reactions are equal in magnitude but opposite in sign.
Entropy on a molecular scale:
S = k lnW
where k = Boltzman constant, 1.38 x 10^-23
S ∝ W
What is the standard entropy, S0?
∆S0 = ∑products - ∑reactants
Relaxed state vs Stretched state:
Relaxed:
molecules move freely,
high entropy,
low enthalpy.
Stretched:
molecules are aligned orderly,
low entropy,
high enthalpy.