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Thermodynamics

Thermodynamics. A Garvey/Ziemba Production. Specific Heat Capacity. The Heat (energy) required to produce a certain temperature per gram of material Specific Heat = heat supplied (mass of object) (Temp Change)

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Thermodynamics

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  1. Thermodynamics A Garvey/Ziemba Production

  2. Specific Heat Capacity • The Heat (energy) required to produce a certain temperature per gram of material • Specific Heat = heat supplied (mass of object) (Temp Change) OR C = q/(m)(∆T) -> q = MC∆T T is in Kelvin, mass in grams, q in Joules. Specifics Heats are often given in problems

  3. Changing States Calculated by Energy = Heat of Fusion/Vaporization x mass of substance This is so easy even JC can do it!! Lets try it!

  4. Sample Problemo • How much heat is required to warm 500g of a solid teacher at -50oC to steam at 200oC? (Teachers are made only of H2O) heat of fusion = 333.5J/g, Vaporization = 2256J/g. specific heat capacities, in order of solid, liquid, gas, hinton, are 2.1, 4.2, and 2.0 J/g x K Lets go!

  5. We can do this….together! • It starts at -50oC and goes to 0o, a change of 50oK • So (500g)(2.1J/gxK)(50o) = 52,500 J • Next for Ice -> water, (500g)(333.5J/g) = 166,750J • Water at 0o to 100o -> (500g)(4.2J/gxK)(100oK) = 210,000J • Now for Water -> Steam (500g)(2256J/g) = 1,128,000J !! • Finally, Steam at 100oC to 200oC -> (500g)(2.0J/gxK)(100oK)=100,000J • Add them up -> 52,500 + 166,750 + 210,000 + 1,128,000 + 100,000 and we get…. • 1657kJ of Death!!!

  6. What we just did looks like this, with 5 steps

  7. Enthalpy change…(BORING!!!!) • The heat transferred into or out of a system (constant pressure) • Enthalpy change is Hproducts - Hreactants • Just remember products minus reactants. It works every time, no matter what unit you are studying. Don’t listen to Mr. Hinton telling me im wrong. • Enthalpies of reaction are the same!!! Sum of the products enthalpys minus sum of the reactants…every time, it works….

  8. The Hess Family Fund • Also know as Hess’s Law • Basicly, if you add reactions, the sum of the reaction’s ∆H’s is the new reaction’s ∆H • If you reverse an equation, the sign on ∆H must change • If you multiply equation, multiply ∆H by same number • Helpful Hint: for all reactions, g = 9.8m/s2

  9. Random

  10. Entropy, Free Energy • The measure of Disorder (symbol is S) • !!! ∆S is Sum of S products - Sum of S reactants • G stands for Gibbs Free Energy, another lovely Thermodynamic Function • ∆G = ∆H - T ∆S • This is Gibb’s Lovely Free Energy Equation. It is (so says the book) very important

  11. Little More Free Energy • ∆G(reaction) = Sum∆G(products) - Sum ∆G reactions • Well I know im surprised • I’d also like to take this time to remind you all the exothermic is a negative ∆H and endothermic is a positive ∆H • Better Late than never, you know

  12. Ther MO and the E constants • We all know the old saying • “∆G = -RT ln K!” • R is 8.314 • K is the THERMODYNAMIC Equilibrium CONSTANT • But hey! • If K>1 Products are favored in a reaction • If K = 1 (Rare) Its at equilibrium • If K < 1 Reactants are favored. • You, Zev and Pat, are never favored.

  13. The Last tired, slide. • Give us a good grade • Give John money • All your Base are belong to the Chemistry Department, in containers kept apart from Acids and Nick’s small thieving hands

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