MCAT Gen Chem 2
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Whether or not a process or reaction can occur.
How fast or slow a process or rection can occur.
Exothermic energy coordinate diagram
Endothermic energy coordinate diagram
Fluid movement caused by the hotter portions of a fluid rising and the cooler portions of a fluid sinking.
- Electromagnetic waves emitted from a hot body into the surrounding environment.
- Light colors radiate and absorb less
- Dark colors radiate and absorb more
- Black Body Radiator - perfect theoretical radiator
- Molecular collisions along a conduit
- Analogous to current flow through a wire or H2O through a pipe
Heat Capacity (definition)
The amount of energy (in Joules or Calories) a system can absorb per temperature unit (J/K or cal/˚C).
Heat Capacity (formula)
C = q/∆T
Specific Heat Capacity (definition)
Is for a given substance only and is defined as the heat capacity per unit mass.
Specific Heat Capacity (formula)
q = mc∆T
First Law of Thermodynamics
- ∆E = q + w
- Work done on the system (+)
- Work done by the system (–)
Second Law of Thermodynamics
- Heat cannot be changed completely into work in a cyclical process
- Entropy in an isolated system can never decrease
Third Law of Thermodynamics
Pure substances at absolute zero have an entropy of zero
Zeroth Law of Thermodynamics
Celsius – Kelvin conversion
- 0˚ C = 273.15 K
- -273.15˚ C = 0 K
- Absolute zero = 0 K
Kinetic Energy of Gasses (formula)
- KE = 3/2kT
- k = Boltzman's constant (1.3806503 e –23 m2 kg s-2 K-1)
- The energy contained within chemical bonds or HEAT
- A measure of the randomness or disorder in a system
- Standard State is 25˚ C (298K) and ∆H = 0
- *For thermodynamics problems
- STP (standard temperature and pressure) is 0˚ Celsius (273K) and 1 atm
- *For gas problems
+ ∆S =
Increased randomness, energy released and available to do work
– ∆S =
Decreased randomness, energy is required to "create" increased order and that energy is thus unavailable to do work
Entropy (∆S) increases with: (5 things)
- 1. Increased number of items/particles/etc. (Gas trumps # of moles or particles. This means that if two moles of reactants makes one mole of product and that product is a gas, it is still +∆S)
- 2. Increased volume
- 3. Increased temperature
- 4. Increased disorder
- 5. Decreased pressure (the higher the pressure the more packing and order of molecules)
Gibbs Free Energy (∆G)
∆G = the amount of "free" or "useful" energy available to do work.
- -∆G = Spontaneous; exothermic
- +∆G = Non-spontaneous; endothermic
Rate Order Graphs
- 0 order: [A] vs. time is linear with slope -k
- 1st order: ln[A] vs. time is linear with slope -k
- 2nd order: 1/[A] vs. time is linear with slope k
- 3rd order: 1/2[A]2 vs. time is linear with slope k
Fundamental Thermodynamic Relation formula
∆G = ∆H - T∆S
- ∆G - Gibbs
- ∆H - Enthalpy
- ∆S - Entropy
- T - Temp K
- (+) means more disorder or increased entropy.
- (–) means more order or decreased entropy.
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