Chem 112 Week of February 15-19 Gibbs Free Energy Notes
Chem 112 Week of February 15-19 Gibbs Free Energy Notes Chem 112
Popular in General Chemistry
Popular in Chemistry
This 3 page Class Notes was uploaded by Rebecca Plummer on Friday February 12, 2016. The Class Notes belongs to Chem 112 at Pennsylvania State University taught by Dr. Raymond Shaak in Spring 2016. Since its upload, it has received 40 views. For similar materials see General Chemistry in Chemistry at Pennsylvania State University.
Reviews for Chem 112 Week of February 15-19 Gibbs Free Energy Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 02/12/16
Rebecca Plummer Dr. Raymond Shaack February 15-19 2016 Free Energy (∆G) Background: ∆H°rxn ∑mol∙∆H° (f oducts) ∑m∙∆H° f eactants) ∆S°rxn m∙∆S° (f oducts) ∑m∙∆S° f eactants) Free energy predicts whether a reaction is spontaneous or not by using enthalpy and entropy. ∆G is negative = spontaneous ∆H ∆S ∆G Spontaneity + Spontaneous at ALL temperatures + + Nonspontaneous at ALL temperatures or + Spontaneous at LOW temperature Nonspontaneous at HIGH temperatures Nonspontaneous at LOW temperatures + + + or Spontaneous at HIGH temperatures ∆G is a state function (the path taken to reach that value does not matter). ∆G focuses only on the system, not the surroundings. ∆G = ∆H T∆S The table above can be made by using this equation. Think mathematically When ∆G = 0… ΔH ∆H = T∆S or ΔS T when ∆G = 0 is the crossover (boiling point, melting point, etc…) temperature When ∆G < 0, the reaction is spontaneous When ∆G > 0, the reaction is nonspontaneous When ∆G = 0, the reaction is at equilibrium When ∆H < 0, the reaction is exothermic (it releases heat meaning it feels hot) When ∆H > 0, the reaction is endothermic (it takes in heat, meaning it feels cold) Units ∆H° = kJ/mol ∆S° = J/molK ∆G° = kJ/mol DO NOT FORGET TO CHANGE ∆S° J TO KJ WHEN DOING CALCULATIONS! ∆G = change in Gibbs free energy Rebecca Plummer Dr. Raymond Shaack February 15-19 2016 ∆G° = change in Gibbs free energy under standard conditions (25°C, 1atm, 1 molar concentration ∆G° rxn∑mol∙∆G° (prf ucts) ∑mol∙∆G° (reacf nts) Just like with ∆H° elements in their standard states (Na(s), Ni(s), H (g), Br (l)) ∆G° will f, 2 2 f equal zero. Free Energy and Equilibrium Reactions spontaneously approach equilibrium The minimum free energy is at equilibrium o Equilibrium is the valley between 2 hills. When you roll a ball down the side of a hill, it will approach the valley. From either side (products or reactants) the ball will approach equilibrium Once equilibrium is established, there is no spontaneous force that will take the reaction out of equilibrium Remember: At equilibrium… o ∆G° = (products – reactants) under standard conditions o ∆G = 0 o They are NOT the same thing!!! Therefore: At equilibrium… T= ΔH o ΔS ∆G Under NonStandard Conditions ∆G = ∆G° + RTln(Q) or ∆G = ∆G° + RTln(k) Remember from Chem 110: At equilibrium the reaction quotient (Q) and the equilibrium constant (Keq are equal to each other αA + βB γC + ẟD Q = K eq[C] [D] / [A] [B] β Q>K you have too many products so the reaction shifts left (producing more reactants) to reach equilibrium Q<K you have too many reactants so the reaction shifts right (producing more products) to react equilibrium ∆G° lnK K Mixture contents 0 0 1 [products] = [reactants] + >1 Mixture is mostly products Rebecca Plummer Dr. Raymond Shaack February 15-19 2016 + <1 Mixture is mostly reactants
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'