3.1.5 Kinetics Knowledge

Question 1

what is collision theory?

Answer 1

Chemical reactions occur when particles of substances collide at energy greater than or equal to the activation energy of the reaction, with the correct particle orientation

Question 2

why are reaction conditions important in collision theory?

Answer 2

the conditions of a reaction impact the collisions of the particles, and can be changed to increase the likelihood of a collision occurring with sufficient energy to react in order to increase rate

Question 3

how can you increase the rate of a reaction, using collision theory?

Answer 3

• Decrease volume of container or increase concentration
• Increase number of particles
• Increase kinetic energy of particles by increasing temperature
• Break up clumps into individual particles
• Use a catalyst

Question 4

why does Breaking up clumps into individual particles increase the rate of a reaction?

Answer 4

Increases surface area of particles, to increase available areas to collide and react

Question 5

what is the Maxwell-Boltzmann Curve?

Answer 5

shows the distribution of molecular energies in a gas at a constant temperature

Question 6

draw an annotated diagram of a general maxwell-boltzmann curve

Answer 6

Question 7

what are the 3 main features of a maxwell-boltzmann curve?

Answer 7

• the area under the curve is equal to the total number of molecules in the sample
• the curve starts at the origin; there are no molecules in the system with 0 energy
• Only molecules with an energy greater than the activation energy can react

Question 8

what is the area under a maxwell-boltzmann curve equal to?

Answer 8

the total number of molecules in the sample

Question 9

why does the curve starts at the origin on a maxwell-boltzmann distribution?

Answer 9

there are no molecules in the system with 0 energy

Question 10

how does increasing temperature affect a maxwell-boltzmann curve?

Answer 10

the peak moves to the right and is lower, whilst the area under the curve remains the same

Question 11

how does increasing temperature affect the rate of a reaction?

Answer 11

• When a substance is heated, thermal energy is transferred to it; this energy is converted into kinetic energy
• The molecules move faster as they have more kinetic energy
• A greater proportion of the molecules have an energy that is greater than the activation energy
• Collisions will occur more often and with greater energy; more successful collisions occur in a given length of time
• the rate of reaction will increase

Question 12

draw a maxwell-boltzmann distribution cirve showing the effect of temperature

Answer 12

Question 13

how does increasing concentration/pressure affect a maxwell-boltzmann curve?

Answer 13

shifted to the right

Question 14

how does increasing concentration/pressure affect the rate of a reaction?

Answer 14

• More molecules of substance occur in the same volume, so they are packed closer together
• collisions between molecules become more likely
• the chances of a collision occurring with energy greater than the activation energy and the correct particle orientation increases
• the rate of reaction increases

Question 15

draw a maxwell-boltzmann distribution cirve showing the effect of temperature

Answer 15

Question 16

how does adding a catalyst affect a maxwell-boltzmann curve?

Answer 16

the addition of a catalyst does not change the distribution of the molecular energies

Question 17

how does adding a catalyst affect the rate of a reaction?

Answer 17

• Catalysts provide an alternative reaction route which requires a lower activation energy
• more molecules in the system have an energy in excess of the new, lower activation energy
• increases the likelihood that collisions occur at sufficient energy; more successful collisions occur in a given length of time
• the rate of reaction will increase

Question 18

draw a maxwell-boltzmann distribution cirve showing the effect of adding a catalyst

Answer 18

Question 19

what are the units of activation energy?

Answer 19

kJ mol^-1

Question 20

define collision frequency

Answer 20

Number of collisions between particles per unit of time

Question 21

define collision energy

Answer 21

Combined energy of colliding particles

Question 22

describe the movement of particles in a given system

Answer 22

Constant random motion

Question 23

define Emp

Answer 23

Most probable value for the energy of particles

Question 24

define Ek

Answer 24

kinetic energy of the particles

Question 25

define E≥Ea

Answer 25

Energy greater than or equal to activation energy

Question 26

If the temperature was increased, what happens to Ea?

Answer 26

stays the same

Question 27

If the temperature was increased what happens to Emp?

Answer 27

position moves to the right

Question 28

If the temperature is increased, what happens to the size of the area under the curve?

Answer 28

remains unchanged

Question 29

When the reaction is heated to a higher temperature, explains what happens to the number of particles having the most common amount of energy

Answer 29

fewer particles with Emp

Question 30

When the reaction is heated to a higher temperature, explains what happens to the number of particles with E≥Ea

Answer 30

more particles with E≥Ea