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13 Cards in this Set
- Front
- Back
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Zeroth Law of Thermodynamics |
When systems are in thermal equilibrium with one another, their temperatures must be the same |
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First Law of Thermodynamics |
total energy of the universe is constant |
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Enthalpy |
Measure of the heat energy that is released or absorbed when bonds are broken or formed at CONSTANT PRESSURE |
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standard conditions vs standard temperature and pressure (STP) |
standard conditions: 25 degrees C STP: 0 degrees C |
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Hess's Law |
the overall change value is equal to the sum of the change values for the various steps of the total reaction |
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Equation to find change in enthalpy |
H=(H products) - (H reactants) for heat of formation H=(H of bonds broken) - (H bonds formed) for bond dissociation energy |
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Second Law of Thermodynamics |
entropy always increases |
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Third Law of Thermodynamics |
absolute zero means zero-entropy. this law describes the least thermodynamically energetic state and therefore the lowest achievable temp |
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Gibbs free energy equation |
G= H-TS T is in Kelvin |
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How to increase entropy |
1. Change phase 2. Increase number of molecules 3. increase volume |
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What is the heat of formation of any element in its natural state? |
0 kj/mol |
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Positive G vs. Negative G vs. G=0 |
(+)G: nonspontaneous/endergonic (-)G: spontaneous/ exergonic G=0: equilibrium |
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How do enthalpy and entropy affect G |
1. if enthalpy and entropy are different charges, G will match the charge of enthalpy 2. If enthalpy and entropy both have the same type of charge, charge of G depends on temperature |
