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Unformatted text preview: most stable form of an element at 1 atm and 25°C CHEM 162 Exam 3 Review Gibbs’ Equation: G = H ‐ T S If G < 0 a spontaneous reaction If G > 0 a nonspontaneous reaction; reverse reaction is spontaneous. If G = 0 reaction is at equilibrium – Given H and S indicate if a reaction is always spontaneous, never spontaneous, only spontaneous at high temperatures or at low temperatures. spontaneous process: occurs without external intervention or stimulus – Recognize that the Ssurr= G=Gibbs free energy – Be able to calculate G° given Gf° data Two Driving Forces for a chemical reaction – Exothermicity: a reaction occurs to form more stable compounds with stronger bonds – Increased Entropy: a reaction occurs to increase the number of available energy states (higher entropy) Standard state conditions: G° = H° ‐ T S° – Be able to calculate G°, H°, T in Kelvins, and/or S° given the other variables – Know standard state conditions Effects of Pressure and Concentration on G: – Use G = G° + RT ln Q where T in Kelvins, R=8.3145 J/mol∙K, and Q=reaction quotient – Know how partial pressure of gases and concentrations of solutions affect G At equilibrium, use: G° = – RT ln K where K=equilibrium constant – Be able to solve for G° or K for any system at equilibrium. – Recognize that the equilibrium point occurs at the lowest value of free energy available to system. A system will move towards equilibrium to achieve the lowest free energy...
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This document was uploaded on 03/22/2014 for the course CHEM 162 at Seattle Central Community College.
- Fall '11