TOPIC 9: KINETICS I

Question 1

What are the conditions for a reaction to take place

Answer 1

1. Particles must collide in the right direction and with the correct orientation to react
2. The particles must collide with enough energy (activation energy)

Question 2

Define activation energy

Answer 2

The minimum amount of energy required for a chemical reaction to occur

Question 3

Describe the effect of temperature on reaction rate

Answer 3

1. increasing the temperature causes particles to have more kinetic energy and will move faster
2. More molecules will have at least the activation energy as particles are colliding more often

Question 4

Describe the effect of concentration on reaction rate

Answer 4

If you increase the concentration there will be more particles in a given volume of the solution so particles will collide more frequently.

Question 5

Describe the effect of pressure on reaction rate

Answer 5

1. increasing pressure of a gas is similar to increasing the concentration in solution
2. At higher pressures there are more particles in a given volume of gas, which increases the frequency of successful collisions

Question 6

Describe the effect of catalysts on reaction rate

Answer 6

Catalysts lower the activation energy by providing an alternate way for bonds to be broken and remade.As the activation energy is lower more particles will have enough energy to react

Question 7

Define reaction rate

Answer 7

The change in the amount of reactant or product per unit time

Question 8

How to calculate the gradient

Answer 8

change in y/ change in x

Question 9

What is a catalyst

Answer 9

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

Question 10

What is a heterogeneous catalyst ?

Answer 10

A heterogeneous catalyst is one that is in a different phase ( state of matter) from the reactants

The reaction happens on the surface of the heterogeneous catalyst so increasing the surface area of the catalyst increases the number of molecules that can react at the same time

Question 11

Describe the process of how which a catalyst speeds up the rate of reaction

Answer 11

1. Reactant molecules arrive at the surface and bond with the catalyst. This is called ADsorption.
2. The bonds between the reactants atoms are weakened and break up. This forms radicals- atoms or molecules with unpaired electrons.These radicals get together and make new molecules
3. The new molecules are then detached from the catalyst. This is called DEsorption

Question 12

What is a homogeneous catalyst ?

Answer 12

A homogeneous catalyst are in the same physical state as reactants

During homogeneous catalysis the reactants combine with the catalyst to make an intermediate species which then reacts to form the products and reform the catalyst

Question 13

Describe the economic benefits catalysts have

Answer 13

1. Catalysts allow the temperature to not be raised as high for the reaction to happen quickly - making it cheaper
2. Using a catalyst can change the properties of a product to make it more useful eg poly (ethene)