Chapter 10 and 11 Flashcards
Hess’s law
enthalpy change for a chemical or physical reaction depends only on initial and final states
the enthalpy change is independent of the reaction pathway
4 rules for manipulation equations in triangle H notation
1) when equation is flipped the sign on triangle H must be reversed
2) compounds that are on opposite sides of equation can only be cancelled out if they are in the same state
3) if the coefficients of the equation are multiplied or divided the same must be dont to their triangle H
4) compounds that are on the same sides of the equation can only be added together if they are in the same state
steps for manipulating equations in triangle H notation
1) write out net equation if not given
2) manipulate equations in order to yield net equation
- flip
- multiply or divide
3) cancel out compounds on opposite sides that are same state and number
4) add remaining compounds to yield net equation
thing to remember when multiply to manipulate an equation in triangle H notation and example
may have to multiply by a fraction to get the right number
Ex) have: 2H20 need: 3H20
multiply by 2/3
Hess’s law formula
H reaction= the sum of nH products- the sum of nH reactants
standard molar enthalpy of elements in standard states
0
2 options for hess’s law calculations
triangle H (long way)
triangle H dot (short way, standard molar enthalpies)
steps for Hess’s law calculations in triangle H
1) carry out steps for manipulating equations in triangle H notation
2) add the component enthalpy changes to obtain the net enthalpy change
steps for Hess’s law calculations in triangle H dot
1) write out net equation if not given
2) determine unknown
3) manipulate Hess’s law formula to solve for unknown
if H dot of something equals 0 what is it’s n value?
O
exception to Hess’s law calculations in triangle H dot
why and what do to
if net equation has 2 or more elements
since there are no standard enthalpies of formation to plug into formula
do it as you would triangle H
efficiency formula
(energy output/energy input) (100)
What to do if Energy input/output isn’t directly given
use Eout or in= Qcan +Qwater
and expand to m(c)(trianglet) to solve
scientific perspective
research
leads to researching and explaining natural phenomena
technological perspective
technology
concerned with the development and use of machines, instruments, and processes that have a social purpose
ecological perspective
environmental effects
considers relationships between living organisms and the environment
renewable energy source
replenishes itself within 100 years
non renewable energy source
fill in
greenhouse gases
fill in
global warming
fill in
economic perspective
financial
gives on the production, distribution, and consumption of wealth
political perspective
legislation
involves vote getting actions and measures
what is the carbon cycle
storing energy in carbohydrates
carbon cycle process
sun—->photosynthesis—->decay
sun
fill in
photosynthesis equation
6 CO2(g)+ 6 H2O(l) + energy —>
C6H12O6(s) + 6 O2(g)
cellular respiration equation
C6H12O6(s) + 6 O2(g) —->
6 CO2(g) + 6 H2O(l) + energy
how do you know a collision is effective
it results in a chemical reaction
what must happen for a collision to be effective
1) steric factor
2) collision must occur with enough energy
what is steric factor
collision must occur with the correct geometrical alignment to bring reactive parts together
what is steric factor important to
important to large molecules with large degrees of steric hindrance
what is activation energy
the minimum amount of energy required for a reaction to occur
abbreviation for activation energy
Ea
activation energy with alligator
E>Ea
another definition or activation energy
the barrier that must be overcome for a chemical reaction to occur
what is transition state
the activated complex when it has Ea
what are the factors increasing the rate of reaction
-increasing the # of molecules that have sufficient energy to react
- properties of reactants
- some reactions occur more slowly because of this
- temp
- catalysts
what is temp directly related to
temp is directly related to the average kinetic energy in a sample
what is maxwell boltzmann distribution used to explain
used to explain reaction rate and temp
the maxwell boltzmann distribution is a plot of ______
’s or particles vs. energy of particles
wha does the maxwell boltzmann distribution show
shows that at diff temps many particles have energies close to the mean
but there are still outliers are are at above or below the mean
what is the area under the curve in the maxwell boltzmann distribution
area under the curve = total energy
what is bond breaking and type of process
kinetic energy is absorbed and stored as potential energy in chemical bonds
endothermic process
what is bond making and type of process
chemical potential energy is released as kinetic energy
exothermic process
what is a catalyst
increases reaction rates by providing alternative pathways for changes without affecting the net amount of energy involved
what does a catalyst provide
provides an alternative pathway that relay ire a lower activation energy than the original pathway
potential energy diagram for exothermic reaction
goes up to down
triangle H= from A+B down to C+D
Ea foreword= from A+B to top of curve
Ea reverse= from C+D to top of curve
transition state=point at top of curve
potential energy diagram for endothermic reaction
goes down to up
triangle H= from C+D to A+B
Ea forward= from A+B to top of curve
Ea reverse= from C+D to top of curve
transition state= point at top of curve
what are the labels of the axis in energy diagrams
x= reaction pathway
y= potential energy
which way do Ea arrows always point on potential energy diagrams
up
what is triangle H always in between on potential energy diagrams
A+ B and C+D
what is Ea forward always inbetween on potential energy diagrams
A+B and curve
what is Ea reverse always in between on potential energy diagrams
C+D and curve
