Topic 10 Flashcards
What is the purpose of potential energy surface plots?
visualize the energy changes as a reaction proceeds
Make predictions about likely pathways and reaction success
What are some variables you can find on a potential energy surface plot?
equilibrium bond lengths, bond lengths at transition states, and minimum activation enegry
What does the dashed line represent on a potential energy surface plot?
The lowest energy pathway from start to finish (minimum energy pathway
If the end point is lower in energy than the starting point, is the reaction endo/exothermic?
exothermic
What is the saddle point on a potential energy surface plot?
The transition state/activation energy
unhappy here because it had to increase in energy
What letter is enthalpy?
H
What letter is entropy?
S
What does the units on gibbs free energy have to be?
au (hartrees)
How many kJ/mol is in a hartree?
2625.5kJ/mol=1au
What is the Eyring-Polanyi equation formula?
k_rxn=(kappak_BT/h)*e^(-deltaG dagger/RT)
What does the Eyring-Polanyi equation tell us?
predicts the rate constant
What is the equation for Gibbs free energy?
deltaG=deltaH-TdeltaS
Where do you find detaG dagger on a reaction coordinate diagram?
from reactant line to the top of the hill
Where do you find deltaGrxn on a reaction coordinate diagram?
from product line to reactant line
Where is the transition state on a reaction coordinate diagram?
The top of the peak
What does it mean when a reaction coordinate diagram has a large ‘hill’?
a big hill makes a slow reaction rate and a small rate constant
If reactants are higher than products, is the reaction ender/exergonic?
exergonic
What is the Y axis on a reaction coordinate diagram?
G
What is is X axis on a reaction coordinate diagram?
rxn coordinates
What does delta G dagger mean?
activation energy
Explain spontaneity.
It does not mean that a reaction is going to happen, it just means that the products are lower thermodynamically/more stable than the reactants
It does not guarantee that the reaction is fast
If gibbs free energy decreases, is the reaction ender/exergonic and is it spontaneous or not?
exergonic and spontaneous
How is the transition state on a reaction coordinate diagram also a ‘saddle point’?
It is unhappy but could have been more unhappy
It is the least unhappy point of the options
The most stable intermediate of a rxn
It is the highest in one respect but the lowest in another
