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OAT - Chem
Chapter - 6 Thermochemistry
Term | Definition |
---|---|
Spontaneous rxn | under a given set of circumstances, the rxn can occur by itself without outside assistance |
System | the particular part of the universe being studied |
surroundings/environment | everything outside of the system |
Isolated System | cannot exchange matter or E with surroundings |
Closed System | can exchange E but not matter with surroundings |
Open System | can exchange both matter and E with surroundings |
Isothermal | Temp of system remains constant |
Adiabatic | No heat exchange occurs, volume remains constant |
Isobaric | Pressure of the system remains constant |
Heat | form of E that can easily transfer to or from a system; from warmer system to cooler system |
Endothermic | positive, heat absorbed |
Exothermic | negative, heat lost |
1 cal | 4.184 J |
Heat Equation | q = mcat |
State Functions | properties whose magnitude depends only on initial and final states of system; P V T |
Enthalpy | H; heat changes at constant pressure; products - reactants |
Standard Heat of Formation | Hf; enthalpy change that occurs if one mole of a compound were formed directly from its elements in standard state |
Hess's Law | enthalpies of rxns are additive |
Heat of Vaporization | from liquid to gas Hv |
Bond E/Bond Dissociation E | avg of the E required to break a type of bond in one mole of gaseous molecules |
Bond Breakage is always... | endothermic |
Bond Formation is always... | exothermic |
Bond E equation | bonds broken+bonds formed (reactants-products) |
Entropy | measure of the disorder or randomness of a system (J/K); products-reactants |
Entropy Spontaneous | means entropy of system increases, more disorder |
Gibbs Free E | G; max amount of E released by a process; G = H - TS |
G is negative | spontaneous, H negative |
G is positive | nonspontaneous, H positive |
G is zero | equilibrium |
If H and S are positive | rxn is spontaneous at high temps |
If H and S negative | rxn is spontaneous at low temps |
When H G or S is followed by a degrees symbol | the rxn occurs during standard conditions of T and P |
G degrees equation | G degrees= -RT ln Keq but when rxn starts Keq becomes Q |
Q | rxn quotient |
G equation | G = G degrees + RT ln Q |
R | gas constant |