Kinetics

Question 1

Meaning of rate of reaction

Answer 1

The change of concentration/amount of reactant or product per unit time

Question 2

How to calculate rate?

Answer 2

(Amount of reactant used/product made )

divide

time

Question 3

meaning of activation energy

Answer 3

the minimum amount of energy required for a reaction to occur is called the activation energy

Question 4

What does the maxwell-distribution show?

Answer 4

It shows the energy in gas particles

Question 5

What does a maxwell-distribution curve show?

Answer 5

• Graph starts at 0,0 as no particles have 0 kinetic energy
• the area under the curve is equal to the total number of molecules
• the peak of curve = the most likely energy of a particle
• slightly right to peak = the mean energy the particles have

Question 6

What is the affect of higher temperature on rate?

Answer 6

• more particles would have energy greater than activation energy.

-peak would be lower than original

• curve will shift to right and will have higher activation energy
• total area under curve remains the same

Question 7

What is the affect of lower temperature on rate?

Answer 7

-curve shifts to the left

-peak is higher

• total area under curve remains the same
• area at activation energy decreases

Question 8

Why is there a faster rate of reaction when temperature is increased?

Answer 8

Small increases in temperature leads to large increases in rate.

This is because higher temperatures allows particles to move around more and collide more often. These more frequent and energetic collisions leads to increases in rate.

Question 9

How does pressure affect rate?

Answer 9

Increasing PRESSURE will increase the rate of reaction.

Particles are closer together and collide more often. There are more frequent collisions and a higher chance of a reaction

Question 10

How does concentration affect rate?

Answer 10

Increasing CONCENTRATION will increase the rate of reaction.

Particles are closer together and collide more often. There are more frequent collisions and a higher chance of a reaction.

Question 11

What is the role of a catalyst?

Answer 11

A catalyst increases the rate of reaction by providing an alternative pathway that has a lower activation energy. The catalyst remains chemically unchanged at the end of the reaction.

• speeds up specific reactions
• used to make products faster (saving money and energy)

Question 12

How does catalyst affect activation energy as displayed on graphs?

Answer 12

• Maxwell-Boltzmann distribution

*activation energy will shift to the left to demonstrate more particles having enough energy to react

• Energy profile diagram
• distance between reactants and peak would be lower due to lower activation energy

Question 13

How can rate be measured in experiments?

Answer 13

1) place a cross on paper and time how long it takes for cross to disappear (precipitate to form)

2) (amount of mass lost)
Place reaction on balance and measure the mass loss as gas is lost.

3) (measuring gas produced)
Measure the amount of gas produced using a gas syringe, measure this over a specified time.