Making Reactions go Faster 2

Question 1

why is it useful to know the energy distribution of molecules

Answer 1

• because molecules in a sample of gas have a wide range of energy levels
• if we work out the energy distribution of molecules you can estimate what fraction of collisions will have the required activation energy

Question 2

what would the curve for the fraction of molecules with energy against energy look like labeled as T1

Answer 2

• it would start at the origin and quickly spike up to a peak
• then would slowly approach the x axis asymptotically

Question 3

where would the most probable energy of the molecules be labeled on the x axis and why

Answer 3

• directly below the peak of the curve

- because that has the highest fraction of molecules at that energy level

Question 4

what would the curve T2, the same reaction, look like compared to T1 if the molecules in T2 had their temperature increased

Answer 4

• the curve would start at the origin and would go up at a lower rate than T1
• the peak would be much broader, horizontally past but vertically below T1’s
• then the drop off part of the curve would always be above T1

Question 5

if the peak of T2 is past T1, why is this so

Answer 5

• the peaks indicate the highest fraction of molecules at that energy level
• the peak being further shows that the highest fraction of molecules have higher energy levels than the molecules in T1

Question 6

would the area under each curve change and why

Answer 6

• no

- because the number of molecule has not changed

Question 7

where would you most likely see the activation energy mark in maxwell-boltzmann distribution curves

Answer 7

near the end of the graph to the right

Question 8

if a mark for the activation energy was made on the T1 and T2 graph, how would you use the graph to deduce which one would have a higher rate of reaction and why

Answer 8

• as the asymptotic part of T2 is above T1, it means that a higher fraction of the molecules at that activation energy mark and beyond for T2 have enough energy in order for a reaction to occur
• as more of the molecules for T2 can react when they collide the rate of reaction would be higher
• therefore meaning that T2 would have a faster rate due to the increase in energy

Question 9

what are the two simple reasons why an increase in temperature results in an increase in the rate of reaction

Answer 9

• particles have more kinetic energy

- particles collide with more force

Question 10

why would the particles having more kinetic energy result in an increase in the rate of reaction

Answer 10

• the particles would be moving around more quickly
• meaning that the frequency of collisions between them increases
• resulting in the frequency of successful collisions increasing

Question 11

why would the particles colliding with more force increase the rate of reaction

Answer 11

• the particles are more likely to reach the activation energy when they collide with more force
• leading to an increase in the frequency of successful collisions

Question 12

what does it mean if solute molecules are trapped in a solvent cage

Answer 12

• the concentration of a solution is quite low making most of the solution a solvent
• this makes the solute molecules to be entirely surrounded by solvent molecules

Question 13

how do solvent cages impact the rate of reaction in solution

Answer 13

• it could increase or decrease it
• you could have less frequent collisions between solute molecules because the solvent molecules get in the way
• but you could also have solute molecules trapped in the same solvent cage
• which would increase the frequency of collisions and therefore successful ones

Question 14

what are the two distinct stages of a reaction in solution

Answer 14

• the molecules have to come together by a process of diffusion into the same solvent cage
• then they have to collide and react