Chapter 7 - Thermodynamics Flashcards
First law of thermodynamics
∆U = Q - W
Q = heat ADDED to system W = work done BY the system
Adiabatic
No heat exchange
Q = 0
∆U = - W
*** Change in internal energy is equal to work done ON THE SYSTEM
Isobaric
Pressure is constant
Isovolumetric
No expansion or compression means no work performed in such a process
∆U = Q
Heat vs temperature ?
Temperature : average kinetic energy
Heat (Q) : transfer of energy from one substance to another …results in differences in temperature
Coffee cup calorimeter, discuss
Constant - pressure
Bomb calorimeter
Constant volume calorimeter
Enthalpy
CHange in heat at constant pressure
= state function
∆H = endothermic. BREAKING BONDS
- ∆H = exothermic reaction FORMING BODS
***doesn’t say anything about sponteaity
What are standard conditions?
298K , 1 ATM
Standard heat of reaction ∆Hºrxn
= ∑∆Hproducts - ∑∆Hreactants
Hess’s Law
Add all the enthalpy together
How do you use bond dissociation energy to measure enthalpy?
Bonds broken- bonds formed
= ∆Hº
Bonds broken = reactants
Bonds formed = products
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Energy absorbed - energy released (same idea)
