3.2.2 The Boltzmann distribution

Question 1

what does a Boltzmann distribution show

Answer 1

it shows how the energy in a system is distributed between the particles

Question 2

what are on the axis of a boltzmann distribution

Answer 2

y = number of particles
x = energy

Question 3

where does the curve start on a boltzmann distribution and why

Answer 3

The curve starts at the origin.
No particles have zero energy

Question 4

what is the area under a curve equal to on a boltzmann distribution

Answer 4

the area under the curve is equal to the total number of particles

Question 5

where does the curve meet the x axis after the origin

Answer 5

There is no maximum energy for a particle - the curve does not meet the x-axis at high energy. The curve would need to reach infinite energy to meet the x axis.

Question 6

Describe the effect of a catalyst on a boltzmann distribution (graph)

Answer 6

A catalyst provides an alternative route with a lower Ea.
This is show by an Ec line before the Ea line showing that in the presence of a catalyst a greater proportion of molecules exceeds the new lower activation energy.

Question 7

Describe the effect of a catalyst on a boltzmann distribution (on the particles)

Answer 7

Compared to Ea, a greater proportion of particles now have energy equal to or greater than the lower Ec. On collision, more particles will react to form products. The result is an increase in the rate of reaction due to more successful collisions

Question 8

describe the effect of temperature on a boltzmann distribution (graph)

Answer 8

At the first temperature a boltzmann distribution is draw including an Ea.
At the second higher temperature a new curve is drawn. As the temperature increases, the average energy of the particles also increase. A small portion of particles still have low energy but more molecules have higher energy. The graph now stretches over a greater range of values. The peak of the 2nd curve is lower and shifted to the right (the peak is at higher energy). the number of particles stays the same so the area under the second curve is the same as the first

Question 9

Describe the effect of temperature on a boltzmann distribution (on the particles)

Answer 9

At a higher temperature:
- More particles have an energy greater than or equal to the Ea
- Therefore a greater proportion of collisions will lead to a reaction, increasing the rate of reaction.
- Collisions will also be more frequent as them particles are moving faster, but the increased energy of the particles is much more important that the increased frequency of collisions