Kinetics Flashcards
(18 cards)
Define activation energy
The minimum energy required for particles to successfully collide to start a reaction
What does the area under thee Maxwell Boltzmann distribution curve represent
The total number of particles
What does the peak of the curve represent
The most probable energy
Where does the mean energy lie in relation to the most probable energy
To the right
Why do some particels have very low energies on the curve
Energy is transferred in collisions, so the particles slow down
Why does the curve go through the origin
There are no particles with no energy
What are the axis for the Maxwell Boltzmann distribution curve
Y: fractional of molecules with energy
X: collision energy
How can a reaction go to completion if few particles have energy greater than Ea
Particels gain energy through collisions
How does an increase in temperature affect the shape of the curve
It is shallower, shift right, less steep peak
Why does an increase in temperature change the shape of the curve
More molecules with higher energies
If temperature is increased, why is the curve shallower than at a lower temperature
The molecules have a wider range of energies at higher temperatures
Define the rate of reaction
The change in concentration of a substance per unit time
What does the gradient represent on a conc vs time graph
The rate of reaction
Why does rate of reaction increase when concentration or pressure is increased
There a more particles per unit volume, so there are more frequent successful collisions
Remember: if a question mentions changing the concentration by a specific amount, mention that the number of particles and number of successful collisions change by this same specific amount
Eg doubling concentration, doubles number of particles, so doubles number of successful collisions
Explain how the Maxwell Boltzmann curve changes when concentration is increased
The curve is higher and area under curve is greater as there are more particles and more particles have energy greater than the Ea
Explain the effect of increasing temperature on rate of reaction
At higher temperatures, the particles have more kinetic energy than energy so collide more frequently and more often with energy greater than Ea. More collisions result in a reaction
How do catalysts increase the rate of reaction
They provide an alternative route with a lower activation energy
