Kinetics

Question 1

What is rate of reaction?

Answer 1

Rate of reaction is the change in the amount of reactant or product over time.

Question 2

What conditions are required in order to make particles react when they collide?

Answer 2

The particles must collide in the right direction

They must collide with at least a certain minimum amount of energy

Question 3

What is the minimum amount of kinetic energy particles need to react with called?

Answer 3

Activation energy

Question 4

What does activation energy do?

Answer 4

Break the bonds between reactant particles

Question 5

What does the area under the Maxwell and boltzmann diagram show?

Answer 5

The total number of molecules in the reaction.

Question 6

What does the peak of the Maxwell -boltzmann diagram show?

Answer 6

The most likely energy for any single molecule.

Question 7

where does the Maxwell-boltzman diagram always start?

Answer 7

the diagram always starts at 0,0 because 0 molecules have 0 energy

Question 8

What is the effect of increasing temperature on the rate of reaction?

Answer 8

If you increase the temperature more particles have at least the activation energy hence more molecules are ready to participate in collisions. Plus each molecule will have more kinetic energy so will be moving around more thus there are more collisions.

Question 9

What will increase the temperature of a reaction do to the Maxwell and Boltzmann diagram?

Answer 9

The Maxwell and Boltzmann diagram will change by shifting too the right, the total number of molecules will be the same so the area under the graph should be the same.

Question 10

What will decreasing the temperature do to the Maxwell and Boltzmann diagram?

Answer 10

The curve will shift to the left as there will be less molecules with the required activation energy.

Question 11

How does changing the concentration affect the Maxwell and Boltzmann diagram?

Answer 11

The area under the curve gets bigger as there are more particles, the particles are closer together in the same volume so collisions - thus chances for particles to react- are more frequent. If there are more molecules there will be a chance that there are more molecules with the required activation energy.

Question 12

How will increasing the pressure of a reaction that involves gasses effect the rate of reaction?

Answer 12

Increasing the pressure will mean that particles are closer together therefore there will be a greater chance of collisions which will mean a faster rate of reaction.

Question 13

What is a catalyst used for?

Answer 13

To increase the speed of a reaction

Question 14

How does a catalyst speed up the rate of reaction ?

Answer 14

A catalyst provides an alternative reaction pathway with a lower activation energy.

Question 15

Is a catalyst changed as result of being used in a reaction?

Answer 15

At the end of a reaction a catalyst is chemically unchanged.

Question 16

Catalysts are not used up in a reaction what is a benefit of this?

Answer 16

A small amount of catalyst can catalyse a huge reaction.

Question 17

If a catalyst is used in a reaction how is the Maxwell and Boltzmann diagram affected?

Answer 17

The shaded region of particles with the activated energy will be larger as there will be more particles with the activation energy as the activation energy is lower hence more particles will have it.

Question 18

Whats the equation for rate of reaction?

Answer 18

Time

Question 19

Briefly - what methods can be used to measure rate of reaction?

Answer 19

• Conical flask on top of white tile with black mark on it
• Change in Mass
• Gas volume given off

Question 20

When would you use the white tile method when measuring rates of reaction?

Answer 20

When the reaction involves the formation of a precipitate

Question 21

When would you use the change in mass method of measuring a rate of reaction ?

Answer 21

When a product is a gas

Question 22

When would you use the volume of mass given off method for measuring rate of reaction?

Answer 22

When the product is a gas

Question 23

Explain the white tile method for measuring rate of reaction

Answer 23

1) You stand a conical flask on top of a white tile that has black mark on it.
2) you then add your reactants to the conical flask and start the stopwatch
3) as the precipitate forms the mark will become harder to see , when the mark can no longer be seen stop the timer
4) the reading on the timer is how long it took the precipitate to form
5) this could then be compared with other results investigated with different variables.

Question 24

What are the draw backs off the white tile method - used to measure rates of reaction?

Answer 24

The idea of when the black marks on the white tile have disappeared is subjective. People may not a free exactly when the mark has “disappeared”.

Question 25

Explain the change in mass method for measuring rate of reaction.

Answer 25

A conical flask is placed on a mass balance , the reactants are poured or put into the flask and a timer is started , you draw a table with one column reading time and the other mass , over equal increments of time you measure the mass of the reaction mixture until you get concordant results for mass which shows the reaction has reached its end point.

Question 26

What are the drawbacks of the mass balance method of measuring rates of reaction ?

Answer 26

The method releases gasses into the air , these gases could be toxic or flammable so it is best to carry out the experiment in a fume cupboard.

Question 27

Explain the measuring the volume of gas evolved method for calculating rate of reaction ?

Answer 27

In this method you use a gas syringe you put the reactants into a conical flask and bung the top with the cork that is connected with secure seals to avoid gas escaping to the gas syringe , you start the timer. You then read of the volume of gas evolved at equal time increments , you know that the reaction has finished when the volume stops increasing. The method is accurate as the mass syringe gives accurate measurements and no toxic or flammable gas escapes into the room it is collected in the syringe.

Question 28

What is a draw back of the gas syringe method for measuring rate of reaction?

Answer 28

If too much gas is evolved then the gas syringe won't be able to measure it , plus gas syringes are quite expensive.