Kinetics

Question 1

what are the factors affecting the rate of reaction

Answer 1

• temperature
• surface area (of solids)
• concentration (of solutions)
• pressure (of gases)
• catalysts

Question 2

how does surface area affect the rate of reaction

Answer 2

Increasing surface area increases rate because more particles are exposed at the surface area and there is a higher frequency of successful collisions

Question 3

how does concentration affect the rate of reaction

Answer 3

Increasing concentration increases rate because there are more particles in a given volume and there is a higher frequency of successful collisions

Question 4

how does pressure affect the rate of reaction

Answer 4

Increasing pressure increases rate becaure there are more particles in a given volume and there is a higher frequency of successful collisions

Question 5

how does temperature affect the rate of reaction

(has the biggest affect out of all the factors)

Answer 5

Increasing temperature increases rate because:
1. particles have more enegy and move more quickly resulting in a higher frequency of collisions
2. higher proportion of particles at or above the activation energy
3. collide more frequently and energetically

Question 6

how does a catalyst affect the rate of reaction

Answer 6

Adding a catalyst increases rate because they offer an alternative pathway for the reaction with a lower activation energy

Question 7

in the Maxwell-Boltzmann Distribution, why does the graph start at the origin

Answer 7

graph starts at the origin as no particles have 0 energy

Question 8

in the Maxwell-Boltzmann Distribution, what does the area under the curve represent

Answer 8

total number of particles

Question 9

on the Maxwell-Boltzmann Distribution graph, where would you find the most probable energy and the mean energy

Answer 9

most probable energy = peak/highest point of graph

mean energy = a little off to the right of the peak

Question 10

in the Maxwell-Boltzmann Distribution, why does the graph never touch the x axis

Answer 10

never touches the x axis as there is no maximum energy

Question 11

in the Maxwell-Boltzmann Distribution, what does the area under the end of the graph represent

Answer 11

proportion of particles at or above the Activation Energy

Question 12

what happens to the Maxwell-Boltzmann Distribution graph when temperature is increased

Answer 12

• area under curve is the same number of particles
• proportion of particles at or above Ea increases
• a wider curve is produced finishing at a higher proportion of particles

Question 13

what happens to the Maxwell-Boltzmann Distribution graph when a catalyst is added

Answer 13

• line is drawn at a lower Ea and so a higher proportion of particles are at or above the Ea
• area under the curve is the same number of particles

Question 14

what are the 3 stages that occur on a graph with volume of gas plotted against time

Answer 14

1. HIGH RATE - high concentration of reactants, high frequency of successful collisions
2. RATE DECREASING - concentration of reactants is decreasing, therefore frequency of successful collisions is also decreasing
3. REACTION STOPPED - rate is at zero, one of the reactants is limiting and has been used up

Question 15

how would increasing temperature affect a rates of reaction graph

Answer 15

increases the rate but does not alter the final volume of gas

Question 16

how would changing surface area affect a rates of reaction graph

Answer 16

• if the same volume of chips are present, however they are smaller/powdered, this will increase the rate but not alter the final volume of gas
• if the volume is doubled and the chips are smaller/powdered, this will increase the rate and double the volume of gas will be produced

Question 17

how would increasing concentration affect a rates of reaction graph

Answer 17

a higher rate would occur and a greater final volume

e.g from 1 mol/dm3 to 2 mol/dm3
this would double the final volume of gas