[10.3] the boltzmann distribution

Question 1

what does a botlzmann distribution curve tell us?

Answer 1

• how the energies of particles are distributed in a sample
• only a small percentage of particles have high energy
• most particles have intermediate energies

Question 2

what are the features of a boltzmann distribution?

Answer 2

• no molecules have zero energy; curve starts at origin
• area under the curve is equal to the number of molecules
• there is no maximum energy for a molecule

• curve does not meet x-axis when there is high energy
• curve would need infinite energy to meet x-axis

Question 3

boltzmann distribution curves and activation energy

Answer 3

• when particles before the activation energy line collide, they will not have enough energy to overcome the activation energy barrier
• when particles after the activation energy line collide, they will have enough energy to overcome the activation barrier
• particles at the peak might collide, but not with enough energy to react

Question 4

draw a normal boltzmann distribution

Answer 4

• most particles have medium energy
• no particles have zero energy
• curve does not meet x-axis
• label activation energy

Question 5

how does a catalyst affect the boltzmann distribution? (draw the curve!)

Answer 5

• catalysts increase rate of reaction by providing an alternative route for the reaction, with a lower activation energy
• the proportion of particles with energy greater than the activation energy increases
• frequency of successful collision (correct orientation and enough energy to overcome the activation energy) increases
• rate of reaction increases

Question 6

how does an increase in temperature affect the boltzmann distribution?

Answer 6

• increasing the temperature increases the average kinetic energy of the particles
• proportion of particles with energy greater than the activation energy increases
• frequency of successful collisions (correct orientation and enough energy to overcome activation energy) increases
• rate of reaction increases

Question 7

how would a boltzmann curve with higher temperature look different?

Answer 7

• lower peak that comes further along
• greater number of particles have higher energy, so line is above original one
• area under the curve should remain the same
• distribution has been shifted towards higher energies

Question 8

how does a decrease in temperature affect the boltzmann distribution?

Answer 8

• decreasing the temperature decreases the average kinetic energy of the particles
• proportion of particles with energy greater than the activation energy decreases
• frequency of successful collisions (correct orientation and enough energy to overcome activation energy) decreases
• rate of reaction decreases

Question 9

how would a boltzmann curve with lower temperature look different?

Answer 9

• higher peak that is earlier on
• fewer number of particles have higher energy, so line is below original one
• area under the curve should remain the same
• distribution has been shifted towards lower energies