10.1-reaction Rates

Question 1

Define rate of a chemical reaction

Answer 1

How fast a reactant is being used up or how fast a product is being formed

Question 2

Define the rate of reaction

Answer 2

The change in concentration of a reactant or a product in a given time

Question 3

Give the formula for rate

Answer 3

Rate = change in concentration / time

Question 4

What are the units for change in concentration ?

Answer 4

Mol dm ^-3

Question 5

What are the units for rate

Answer 5

Mol dm ^-3 S^-1

Question 6

What are the 4 factors that can affect a chemical reaction ?

Answer 6

• concentration ( or pressure when reactants are gasses )
• temperature
• use of a catalyst
• surface area of solid reactants

Question 7

What does collision theory state ?

Answer 7

Two reacting particles must collide for a reaction to occur

Question 8

What are the conditions of effective collisions ?

Answer 8

• the particles collide with correct orientation
• the particles have sufficient energy to overcome the activation energy barrier of the reaction

Question 9

How does increasing the concentration affect the rate of reaction ?

Answer 9

• when the conc of a reactant is increased = ROR generally increases
• increase in concentration = increases the number of particles in the same volume
• the particles are closer together and collide more frequently
• in a given period of time there will thus be more effective collisions
• resulting in a higher rate of reaction

Question 10

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

Answer 10

• when a gas is compressed into a smaller volume the pressure of a gas is increased = ROR also increases
• the conc of the gas molecules increases as the same number of gas molecules occupy a smaller volume
• gas molecules are closer together and collide more frequently
• thus leading to a more effective collisions in the same time

Question 11

What are the methods for following the progress of a reaction ?

Answer 11

• monitoring the decrease in concentration of a reactant
• following the increase in concentration of a product

Question 12

What does the method chosen depend on ?

Answer 12

• depends on the properties and physical states of the reactants and products In the reaction
• gas volume
• mass of reactants
• colour
• mass of products

Question 13

How to monitor reactions that produce gases ?

Answer 13

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

Question 14

What is the relevance of volume of gas and mass lost ?

Answer 14

They are both proportional to the change in concentration of a reactant or product