Rates of reaction (6.1) (M)

Question 1

How do you calculate rate of reaction?

Answer 1

quantity of reactant used or product formed / time taken

Question 2

How do you calculate mean rate of reaction?

Answer 2

quantity of reactant used or product formed / time taken - for the whole reaction

Note: the line is likely to be extended once the reaction is complete (disclude this from the calculation)

Question 3

How do you calculate the rate of reaction at a specific point?

Answer 3

Draw a tangent and calculate gradient

Question 4

5 needed

Which factors increase the rate of reaction?

Answer 4

By increasing:

• the concentrations of reactants in solution
• the pressure of reacting gases
• the surface area of solid reactants
• the temperature
• the presence of catalysts

Question 5

What does collision theory state?

Answer 5

Chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.

Question 6

What is activation energy?

Answer 6

The minimum amount of energy that particles must have to react

Question 7

How does increasing the concentration of reactants in solution, the pressure of reacting gases, and the surface area of solid reactants increase the rate of reaction?

Answer 7

increases the frequency of collisions (more of particle is exposed for SA for same mass, more particles per unit volume to collide with for pressure/conc) and so increases the rate of reaction

Question 8

How does increased temperature increase the rate of reaction?

Answer 8

The particles move faster.

This increases the frequency of collisions and makes the collisions more energetic (collisions have energy greater than activation energy in some mark schemes)

Question 9

What do catalysts do in chemical reaction?

Answer 9

Catalysts change the rate of chemical reactions but are not used up during the reaction (reduce activation energy)

Question 10

Why can’t we use the same catalyst for every reaction?

Answer 10

Different reactions need different catalysts

Question 11

What type of catalyst are enzymes?

Answer 11

Biological catalysts

Question 12

What is the role of enzymes?

Answer 12

Enzymes act as catalysts in biological systems

Question 13

How do catalysts increase the rate of reaction?

Answer 13

By providing a different pathway for the reaction that has a lower activation energy

Question 14

Draw a reaction profile for a catalysed reaction

Answer 14

As below

Question 15

4 marker

In a reaction between calcium carbonate and hydrochloric acid, how does the rate of reaction change as the reaction progresses?

Answer 15

acid particles used up

so concentration decreases

so less frequent collisions

so rate decreases