TOPIC 9: Reaction kinetics

Question 1

What is ‘rate of reaction’?

Answer 1

It is the change of the concentration of a reactant or product over a period of time.

Question 1

What factors affect rate of reaction?

Answer 1

1. Pressure
2. Temperature
3. Concentration
4. Surface Area

Question 2

How do you measure rate of reaction?

Answer 2

METHOD 1:
- Use sodium thiosulfate and add it to acid in a beaker. Place the beaker on a white tile with an X marked underneath it and time how long it takes for the beaker to change colour

METHOD 2:
- Use sodium thiosulfate and add it to acid in a beaker. You can then use a colorimeter to measure the color change more accurately and measure how long it takes for the colorimeter to detect the change in colour.

Question 3

How do you calculate rate of reaction on a graph?

Answer 3

Draw a tangent at the specific point that they want the rate of reaction.

Question 4

What is the most important thing to remember with rate of reaction?

Answer 4

The molecules must collide with the correct orientation and with the required activation energy.

Question 5

What do catalysts do?

Answer 5

They provide an alternate reaction pathway with less activation energy so a higher portion of molecules will be able to react. It is important to note that catalysts don’t change the reaction at all or the yield of products.

Question 6

How does changing temperature affect rate of reaction?

Answer 6

Increasing temperature increases the thermal energy so the average kinetic energy of particles increases therefore they move faster. This results in more frequent successful collisions with activation energy and correct orientation.

Question 7

How does changing pressure affect rate of reaction?

Answer 7

Increasing pressure means more particles are in the same volume so there are more frequent successful collisions with activation energy and correct orientation.

Question 8

How does changing surface area affect rate of reaction?

Answer 8

Increasing surface area means there are more points of contact with the reactants so there are more frequent successful collisions with activation energy and correct orientation.

Question 9

What does the boltzmann distribution graph show?

Answer 9

It shows the number of molecules with a specific amount of energy. The area under the graph represents the number of particles (or number of molecules) in the gas.

Question 10

What effect does temperature have on the boltzmann distribution graph?

Answer 10

At higher temperatures, the kinetic energy of all molecules will increase. This means:
1. The graph will lower and shift to the right
2. The area above Ea (activation energy) will be greater
3. The overall area under the curve will remain the same as the number of molecules in the sample does not change