The Rate and Extent of Chemical Change: Rate of Reaction

Question 1

What are the two formulae to calculate rate of reaction?

Answer 1

quantity of products formed
—————————————
time taken (s)

quantity of reactants used
————————————-
time taken (s)

Question 2

What are the factors that affect the rate of chemical reactions?

Answer 2

• temperature
• concentration/pressure
• surface area
• presence of catalyst

Question 3

What does collision theory state?

Answer 3

In order for particles to react they must collide with one another with suffiecient energy. This energy required it called the activation energy.

Question 4

How does increased temperature increase the rate of reaction?

Answer 4

• as temperature increases, the particles gain more energy
• this means they’ll move faster
• therefore they will collide more frequently
• they will also collide with more energy due to point 1
• this means they’re more likely to exceed the activation energy
• therefore overall there will be a higher rate of successful collisions
• and so a higher rate of reaction

Question 5

How does increased concentration/pressure affect the rate of reaction?

Answer 5

• there are more particles per unit volume
• more frequent collisions
• increases rate of reaction

Question 6

How does increased surface area affect the rate of a reaction?

Answer 6

• an increased surface area : volume ratio means increased rate of reactiom
• this is due to there being a larger area over which collision could take place
• this means the frequency of the collisions is higher

Question 7

What are catalysts?

Answer 7

Substances that speed up a reaction without being used up the reaction themselves.

Question 8

How does the presence of a catalyst increase the rate of reaction?

Answer 8

• a catalyst lowers the activation energy by providing an alternative reaction pathway
• this means there will be a higher proportion of successful collisions

Question 9

What metals are frequently used as catalysts?

Answer 9

transition metals