Rates of Reaction

Question 1

Explain what is meant by the term catalyst

Answer 1

• substance which speeds up the rate of a reaction

- but is not used up and remains unchanged at the end

Question 2

Explain in terms of particles and collisions why the rate of reaction increases when concentration of one of the reactants is increased

Answer 2

• more particles in the same volume

- so more frequent collisions between particles

Question 3

State how the graph shows that line B gives the results for the larger marble chips

Answer 3

• line is less steep

Question 4

During any reaction reactants are used up and rate of reaction decreases

explain why the rate of reaction decreases

Answer 4

• fewer particles as the reactants are be around used up - fewer particles to react
• results in lower frequency of collisions so less successful

Question 5

Which one of these graphs shows the mass of the catalyst as the reaction takes place?

Answer 5

C

Question 6

Explain why it is not possible to predict what the rate of experiment 2 will be compared to experiment 1

Answer 6

• decrease in temperature will cause a decrease in the rate of reaction
• increase in pressure will cause an increase in rate of reaction
• changes have opposite effects so not possible to tell which had a greater effect

Question 7

When zinc powered is used instead of zinc particles the reaction is faster

explain why the reaction is faster when zinc powder is used

Answer 7

• zinc powder has larger surface area

- therefore more frequent collisions between particles