Things you need to know FOR the final Flashcards
What is thermochemistry?
The study of Enthalpy(head) changes om a chemical reaction that walways involves a system + surroundings to create.
What are the types of systems?
Open, Closed and Isolated
Temperature in thermochem?
Celcius or Kelvins
What happens in an Open System?
Mass and energy are exchanged
What is enthalpy?
Heat flow measured under conditions of constant
What happens in an Isolated System?
Neither are exchanged
What happens in a Closed System?
Only energy is exchanged
What are thermochem units?
Temperature, Heat, Enthalpy
Heat in thermochem?
is Q and is in Joules/ Kilojoules
Enthalpy in thermochem?
Is H and is also in Joules/ Kilojoules
What is a spontaneous process?
A process that occurs in a system left to itself. It does not mean that it is fast.
1st law of energy flow is?
When energy can be converted from one form to another, but cannot be created/destroyed (ice to water, water to gas)
What do downhill reactions mean?
Exothermic, it is giving off heat and causing the temp to go up
What do uphill reactions mean?
Endothermic, is absorbing heat and is causing the temp to go down
2nd law of energy flow is?
Explains why chem reactions who in a certain direction. It is based on entropy
Whats more spontaneous, gas or liquid?
Gas
Whats more spontaneous, solid or liquid?
liquid
Whats more spontaneous, gas or solid?
gas
How to calculate ΔS of rxn?
Products - Reactants
What is the second law of Entropy?
The entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process.
Equilibrium in entropy?
ΔSuniv = ΔSsys +ΔSsurr = 0
Spontaneous reactions in Entropy?
ΔSuniv(+)= ΔSsys(-)+ΔSsurr(+)>0
How to calculate ΔSsurr?
-(ΔHsys)
———–
T
How to calculate ΔG?
ΔH-TΔS
How to calculate ΔH from ΔHf?
(Products-reactants) *(# of moles)
Spont., Nonspont., or Temp dependent?:
ΔH(enthalpy)= -
ΔS(entropy)= -
ΔG= +
Spontaneous, but only at low temperatures
Spont., Nonspont., or Temp dependent?:
ΔH(enthalpy)= -
ΔS(entropy)= +
ΔG= -
Always spontaneous
How to calculate ΔS?
(Products-reactants) *(# of moles)
Spont., Nonspont., or Temp dependent?:
ΔH(enthalpy)= +
ΔS(entropy)= -
ΔG= +
Always nonspontaneous
Spont., Nonspont., or Temp dependent?:
ΔH(enthalpy)= +
ΔS(entropy)= +
ΔG= -
Spontaneous, but only at high temperatures.
How to find T when given ΔH and ΔS?
ΔH/ΔS
What is the second way to find ΔG?
ΔG of rxn= Sum of all Products - Sum of all Reactants
or final-initial
How to calculate ΔSvap?
Tb
How to find T if given ΔHfus and ΔSfus?
ΔHfus/
ΔSfus
How to calculate ΔSfus?
Tm
How to calculate reaction rate?
Change in # of moles/
Change in time
What variables affect rate?
The type of reaction it is, Concentration, time, temp, pressure/volume, a catalyst or the lack of one.
If ΔG is large and negative what must be true?(When ΔG< 0)
Products are favored at equilibrium and is Spontaneous
If ΔG is small and positive what must be true? (When ΔG> 0)
Is nonspontaneous and reactants are favored
Rate law for a first order reaction?
Rate=k[A]
Rate law for a second order reaction?
Rate=k[A]^2 or Rate=k[A][B]
Rate law for a 0 order reaction?
Rate=k
Integrated rate law for 2nd order reaction graph info?
Will be 1/[A]t by time and is pointed up from left to right
Integrated rate law for 1st order reaction?
ln([A]t/[A]0)=-kt
Integrated rate law for 1st order reaction graph info?
will be ln[A]t by time, is pointed down from left to right
Integrated rate law for 1st order reaction?
ln[A]t=-kt+ln[A]0
Integrated rate law for 2nd order reaction?
1/ln[A]t=kt+1/ln[A]0
Integrated rate law for 0 order reaction?
[A]t=-kt+[A]0
What does [A]0 stand for?
Concentration at the initial time or at time of 0
Integrated rate law for 0 order reaction graph info?
Will be [A]t by time and is pointed down from the left to the right.
What does [A]t stand for?
Concentration at that specific time.
How to find rate in general?
change in [A]/ change in time
what does k =?
rate constant
