Chem 2

used to develop criteria for predicting the direction of a chemical reaction
is the reaction spontaneous? occuring on it's own without added work? and Time?

Study of heat and work

energy that is transferred by system-surrounding until thermal equilibrium is established. (not state functions)

energy transfer between system and surrounding but results in (w=fxd) movement.
(not state functions)

the universe

specific part of the universe that is of interest

3 types of system

matter and energy transfer can occur between system and surroundings

only energy transfer can occur. Ex: earth

no matter or energy transfer can occur ex. thermos bottle
q+w

depends of the present state of the system not how it got there. (final + initial condition)

measures the energy absorbed or released as heat in a chemical or physical change

absorbs energy

releases energy, system releases energy to the surrounding

measure of avg kinetic energy of the particles in a sample. higher the temp, molecules move faster
KE = 1/2 mv^2

amount of heat reqd to change temp. (intensive) always constant, the mass/ change in temp is a ratio.
heat=mass x change in temp x specific heat capactiy
(J) (g) (deg C) (J/g deg C)

measure of systems capactiy to take up heat (extensive property)
C=q/change in temp

Law of conversion of energy. energy cannot be created nor destroyed.
qsyst + qsurr= 0
qsyst = -qsurr

Energy = q+w
q>0 toward the system (endo) heat absorbed w>0= work done on the system by the surr.
q<0 away from the system (exo) heat released w<0= work done by the system on the surr

H(heat of rxn)=u + pv
-measured using a calorimeter

energy available to do work

delta H= Hfinal - H initial
delta H>0 endothermic
delta H<0 exothermic
directly proportional to the amount of reactions/products involved

allow chemists to find "H" (enthalpy) for reactions that cant be perfomed directly

in any spontaneous process, the entropy (s) "disorder" of the universe is increasing. and remains unchanged in an equilibrium process.
1. s<l<g
2. increase in s, increase in T, particles moving faster
3. delta S = Sprod - Sreact

products are favored

delta H<0, delta S>0

delta G
if (-) spontaneous
if (+) non spontaneous
if (=0) equal
delta G=delta H-TdeltaS
(for S to be negative, temp needs to be low)

delta H <0, delta H>0
delta S <0, delta S>0 all depends on temperature

Factors that can change a non spontaneous rxn to spontaneous rxn:

every substance has a finite(f) entropy, but at zero Kelvin, the entropy may become zero as in the case of a perfect crystal

speed of any change over a period of time
amount of mol (react)/ time

atoms, ions and molecules react to form products when they collide provided particles have enough kinetic energy.

factors affecting reaction rates

if stress is applied to a system in dynamic equlibrium, the system changes to relieve the stress

3 types of stresses