Chemistry 1150 chapter 6
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Thermodynamics is the study of
 heat and its
 transformations

Thermochemistry is a branch of thermodynamics that deals with
 the heat involved with chemical and
 physical changes.

When energy is transferred from one object to another, it appears as
work (w) and/or as heat (q).



1 Calorie (Cal)= c
1 kilocalorie

Delta Euniverse
Delta Esystem + Delta Esurroundings

Delta E
Efinal  Einitial = Eproducts  Ereactants

∆E = First Major Equation
q + w (heat +work)?

PV work
Pressure Volume Work

•PV work:
created because of
volume change against an external pressure

Work = External Pressure x Change in
Volume
w = ─PDV

SOME IMPORTANT TYPES OF ENTHALPY CHANGE
C4H10(l) + 13/2O2(g) > 4CO2(g) + 5H2O(g)
heat of combustion (DHcomb)

SOME IMPORTANT TYPES OF ENTHALPY CHANGE
NaCl(s)>NaCl(l)
heat of fusion (DHfus)

SOME IMPORTANT TYPES OF ENTHALPYCHANGE
C6H6(l)>C6H6(g)
heat of vaporization (DHvap)

SOME IMPORTANT TYPES OF ENTHALPY CHANGE
K(s) + 1/2Br2(l)> KBr(s)
heat of formation (DHf)

Second Major Equation
Heat Equation q = mass x cs x ∆T (Always
TF – TI!)
q = mass x cs x ∆T (Always TF – TI!)

AMOUNT (mol) of compound A
molar ratio from balanced equation
goes to
AMOUNT (mol) of compound B

AMOUNT (mol) of compound B goes to
DHrxn (kJ/mol)
HEAT (kJ) gained or lost

Third Major Equation
I don't get what its suppose to be exactly

since DE = q + w, we can determine DE (System) by...
measuring q and w

What do q and w stand for?
 q The heat transferred into/out of the system
 wThe work done by/on the system.

A state function
Change in altitude depends only on the difference between the initial and final values, not on the path taken.

Hess's Law
The change in enthalpy for a stepwise process is the sum of the enthalpy changes of the steps. (Add up the changes for your total answer)

Fourth Major Equation!
 DH0rxn = S mDH0f(products) S nDH0f(reactants)
 ??? Study this outside the cards I don't get it, I think it has something to do with hess's law