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)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

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!

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!

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!!!

What we just did looks like this, with 5 steps

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….

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

Random

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

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

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.

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