Topic 9 Kinetics

Question 1

What is rate of reaction

Answer 1

The change in concentration of a reactant per unit time

Question 2

what is the equation for rate of reaction

Answer 2

Change in Conc / time

Question 3

what is the 2 requirements of the collision theory

Answer 3

• The 2 molecules must collide with enough energy to cause a reaction (activation energy)
• The 2 molecules must collide in the correct orientation

Question 4

what is activation energy

Answer 4

The minimum energy required by colliding particles for a reaction to occur.

Question 5

what is the activation used for

Answer 5

It’s used to break existing bonds in the original molecule.

Question 6

Why is correct orientation of molecule important for reaction to take place

Answer 6

The reaction can only take place if the 2 molecules collide in the right manner/direction.

Question 7

what does the Maxwell-Boltzmann Distribution Curve show

Answer 7

Shows the energy in gas particles

Question 8

How does a higher temperature effect rate of reaction

Answer 8

• At a higher temperature the particles gain more KE.
• This means that the particles can move around more which means more often + energetic collisions.

Question 9

what are the 4 distinct changes to the maxwell-boltzmann distribution model if the temperature is higher

Answer 9

1. Curve shifts to the right
2. Peak is lower
3. The area under the curve is the same
4. Area under curve beyond the A.E increases

Question 10

how does higher concentration effect ROR

Answer 10

• There are more molecules of substance in the same volume meaning they are pakced closer together
• Therefore collisions between molecules become more likely and the probability of a collision occuring with greater A.E increases

Question 11

How does pressure effect ROR

Answer 11

• The same number of molecules in smaller volume means they are packed closer.
• This means there will be more frequent + successful collsions which have greater A.E

Question 12

How does surface area affect ROR

Answer 12

• Increasing the surface area increases the number of exposed reactants particles
• This means there are more frequent successful collisions

Question 13

what is a catalyst

Answer 13

Is a substance that increases the rate of reaction without being used up by providing an alternative route for reaction which requires lower activation energy. This means more particles have equal to or more energy than activation energy, allowing reaction to take place.

Question 14

what is different about the maxwell-boltzmann distribution with catalyst and what does it allow

Answer 14

it has lower A.E requirements which means more particles have enough energy to react

Question 15

what is a hetrogenous catalyst

Answer 15

Catalysts which are in different phase from the reactants.

Question 16

what is adsorbtion

Answer 16

attracting and holding molecules on surface

Question 17

how does a hetrogenous catalyst react with reactants

Answer 17

Reactants bond with the active sites on the surface of the catalyst (adsorbtion)

This results in the bonds between reactants to weaken and break to form radicals, which then react with each other to make new substances.

The new molecules are then released from the surface of the catalyst in process called desorption

Question 18

how will increasing S.A effect ROR

Answer 18

Increasing the surface area of the heterogeneous catalyst will increase the rate of reaction as more particles can react with the surface of catalysts in the active sites at the same time.

Question 19

how will pressure of catalyst effect ROR

Answer 19

Increasing pressure has limited effect on rate of heterogeneous catalysed reaction because reaction takes place on surface of catalyst. All the active sites on catalysts are already used up with reactants, so higher pressure won’t have an effect.

Question 20

benefits of using catalyst in reaction (2)

Answer 20

Lower temperature required, meaning less money is spent on energy and less carbon and other emissions are produced.

Enables alternative reaction with higher atom economy, meaning fewer raw materials needed and less waste produced.