Unit 4 Flashcards
Thermodynamics
Study of Energy and How it Changes
Potential
Energy possessed by an object
Gravitational
Electrical
Chemical
1st Law of Thermodynamics
Energy must be conserved
2nd Law of Thermodynamics
Entropy of Universe is increasing
3rd Law of Thermodynamics
Anytime heat is added, entropy increases
Exothermic
System gives off heat
Bonds are formed
Endothermic
System takes in heat
Bonds are broken
Qrxn =
- Qsurr
Factors that Affect Rate
States of Reactants (rate goes up with surface area)
Reactant Concentration
Reaction Temperature
Introduction of Catalyst
Average Rate =
Δ[A] / Δt
Instantaneous Rate
Must have graph of Concentration vs. Time
Draw tangent line to fit point, make triangle to find Δ[A} and ΔT
Differential Rate Law
Rate vs. Concentration
Integrated Rate Law
Concentration vs. Time
[A] vs. Time yields Straight
Zeroth Order
ln[A] vs. Time yields Straight
First Order
1 / [A] yields Straight
Second Order
Zeroth Order Reaction Rate Law
[A] = -kt + [A]i
First Order Reaction Rate Law
ln( [A]i / [A] ) = kt
Second Order Reaction Rate Law
1/ [A] = kt + 1/ [A]i
Zeroth Order Half Life
t half = [A]i / 2k
First Order Half Life
t half = .693/ k
Second Order Half Life
t half = 1/ k[A]i
Collison Model
States chemical reactions occur when molecules collide with each other
Rate Collison raises expoentially with temperature
Molecules must have proper orientation
Molecules must be going fast enough, known as activation energy
Molecularity
Describes # of particles that must collide at once for reaction to occur
Entropy
Measure of disorder/randomness
ΔS univ =
ΔS sys + ΔS surr
if ΔS Univ is positive, it is spontaenous
ΔS surr =
-ΔH / T
ΔG =
ΔH - TΔS
