A4 Kinetics I

Question 1

Describe how decreasing concentration affects rate

Answer 1

• Decreases rate
• Less particles per unit volume
• Less frequent collisions
• Less successful collisions per unit time

Question 2

Describe how increasing concentration affects rate

Answer 2

• Increases rate
• More particles per unit volume
• More frequenct collisions
• More frequent collisions per unit time

Question 3

Describe how increasing pressure affects rate

Answer 3

• Increases
• Increases the concentration of molecules
• More frequent collisions
• More successful collisions per unit time

Question 4

Describe how decreasing pressure affects rate

Answer 4

• Decreases rate
• Decreases the concentration of molecules
• Less frequent collisions
• Less successful collisions per unit time

Question 5

Describe how increasing temperature affects rate

Answer 5

• Increases rate
• Particles have more kinetic energy
• More particles have energy greater than the activation energy
• More successful collisions per unit time

Question 6

Describe how decreasing temperature

Answer 6

• Decreases rate
• Particles have less kinetic energy
• Less particles have energy greater than the activation energy
• More successful collisions per unit time

Question 7

Describe a method to calculate initial rate

Answer 7

• Plot a XXX against time graph
• Draw a tangent at t=0s
• Gradient of tangent = XXX/Time
• Gradient of tangent = initial rate

Question 8

Define a catalyst

Answer 8

• Lowers activation energy of reaction
• By providing an alternative route for the reaction
• Meaning a greater number of molecules have energy that’s greater than the activation energy

Question 9

Describe the difference between homogenous and heterogenous catalysts

Answer 9

• Homogenous catalysts are in the same physical state as the reactants
• Heterogenous catalysts are in a different physical state to the reactants

Question 10

When is it difficult to classify if a catalyst is homogenous or heterogenous

Answer 10

When the reactants have different physical states

Question 11

Describe and explain the importance of catalysts

Answer 11

• Allow reactions to occur at lower temperatures
• Reduce energy demand from combustion of fossil fuels
• Less CO2 produced

Question 12

Describe the apparatus and method to investigate rate with volume

Answer 12

• Weigh excess metal using mass balance
• Measure volume of acid using measuring cylinder
• Mix metal and acid in concial flask
• Measure gas volumes from gas syringe at regular intervals
• Example: 15s using stopwatch
• Continue until no further change in volume

Question 13

Describe the apparatus and method to investigate rate with mass

Answer 13

• Weigh excess mass of metal using mass balance
• Measure volume of acid with measuring cylinder
• Mix metal and acid in concial flask
• Measure initial mass
• Re-weigh at regualr time intervals
• Example: 15s using stopwatch
• Continue until no further change in mass

Question 14

Draw a Maxwell-Boltzmann graph, and show and explain how an increased temperature would affect this

Answer 14

• Increasing temperature means that there is a greater area under the curve above the activation energy
• A greater number of molecules have energy greater than the activation energy

Question 15

Describe and show how a catalyst affects a Maxwell-Boltzmann distribution graph

Answer 15

• Greater area under the curve with energy above the activation energy
• A greater number of molecules have energy greater than the activation energy