A4 - Kinetics I

Question 1

How does increasing the concentration affect the rate of reaction?

Answer 1

• Increasing the concentration generally increases the rate of reaction
• There is an increase in the number of particles in the same volume
• The particles are closer together and collide more frequently
• In a given period of time there are therefore more successful collisions

Question 2

How does increasing the pressure of a gas affect the rate of reaction?

Answer 2

• If the pressure of a gas is increased the rate of reaction increases
• The concentration of the gas moleucles increases as the same number of gas molecules occupy a smaller volume
• The gas molecules are closer together and collide more frequently
• Leading to more successful collisions in the same time

Question 3

What ways can you determine the rate of reaction is the reaction produces a gas?

Answer 3

• Monitor the volume of gas produced at regular time intervals using gas collection
• Monitor the loss of mass of reactants using a balance

Question 4

What is an intermediate?

Answer 4

A species formed during a reaction that reacts further and is not present in the final products.

Question 5

A catalyst may react with a reactant to form what?

Answer 5

An intermediate

Question 6

Define a catalyst:

Answer 6

A substance that increases the rate of a chemical reaction without being used up in the process; a catalyst provides an alternative route for the reaction with lower activation energy.

Question 7

What is a homogenous catalyst?

Answer 7

It has the SAME physical state as the reactants.

Question 8

Do homogenous catalysts form intermediates?

Answer 8

Yes - the intermediate then breaks down to give the product and regenerates the catalyst.

Question 9

What is a heterogenous catalyst?

Answer 9

It has a DIFFERENT physical state from the reactants.

Question 10

How do heterogenous catalysts work?

Answer 10

Reactant molecules are adsorbed (weakly bonded) onto the surface of the catalyst, where the reaction takes place. After the reaction, the product moleucles leave the surface of the catalyst by desorption.

Question 11

What are the economic effects of catalysts?

Answer 11

Can cut energy costs (as the chemical process requires less energy) and can increase profitability too (as there can be higher atom economies).

Question 12

How do catalysts improve sustainability?

Answer 12

If a chemical process requires less energy, then less electricity or fossil fuel is used. Using less fossil fuel will cut emissions of carbon dioxide and reduce global warming.