3.1 Physical Chemistry: .5 Kinetics

Question 1

the collision theory suggests that a reaction will only take place if three conditions are met.

what are these conditions?

Answer 1

1. ) the reactants collide
2. ) The collisions occurs with a certain minimum energy, know as the activation energy
3. ) the collision has the correct collision geometry

Question 2

what is meant by rate?

what are the units?

Answer 2

rate is a measur of how much the concentration of substrate changes per unit time

moldm^-3 s^-1

Question 3

what is the eqaution for working out rate?

Answer 3

rate= amount of reactant used or product formed/ time taken

Question 4

what is meant by the activation energy?

Answer 4

the minimum energy needed to start a reaction

Question 5

why is it that most collisions do not lead to a reaction?

Answer 5

-

Question 6

what does the Maxwell-Boltzmann distribution show you?

Answer 6

it tells us about the distribution of energy amongst the particles

Question 7

explain how increasing the concentration of the reactants in a reaction affects the rate of reaction

Answer 7

• increasing the concentration of products increases the collision frequency
• leading to a faster rate of reaction
• i.e more successful collisions per second, per cm³

Question 8

how does doubling the concentration affect the rate of reaction? represent this in a equation

Answer 8

• doubling the concentration doubles the number of particles per cm³
• therefore doubling the number of successful collisions per second,
• so the collision frequency is doubled meaning the rate of reaction is 2 times faster

[C₂ = 2 x C₁]

Question 9

show an increase an concentration (x2) on a molecular distribution graph

and a formula to represent this

Answer 9

Question 10

how can an increase in pressure be achieved

Answer 10

-increasing the pressure of a gas can be achieved by reducing its volume whlist leaving all particles the same

Question 11

explain how increasing the pressure would affect the rate of reaction

Answer 11

• increasing pressure has the same effect as increased concentration
• so it leads to an increased collision frequency which leads to a faster rate of reaction
• i.e more successful collisions per second, per cm³

Question 12

on molecular energy distribution graph why does the curve start at (0,0)

Answer 12

because no molecules have 0 energy

Question 13

what is the EMP on a molecular energy distribution graph

Answer 13

most probably energy

Question 14

what is the E mean on a molecular energy distribution graph?

Answer 14

the average energy

Question 15

what does the area under a molecular energy distribution graph equal to?

Answer 15

the total number of molecules

Question 16

explain how does an increase in surface area affects the rate of reaction?

Answer 16

• when a solid reacts, only the particles on the surface are available for reaction
• if the particles i broken up into smaller pieces it’s surface area gets bigger and more particles (surfaces) are available for collisions
• therefore the collision frequency increases as there are more successful collisions per second
• increasing the rate of reaction

Question 17

explain how what would happen to the rate of reaction if there was a rise in temperature

represent this in a graph

Answer 17

• a rise temperature will result in an increased rate of reaction
• this is because at a higher temperature there are more particles with energy greater than or eqaul to the activation energy
• therefore more successful collisions per second

Question 18

what is a catalyst?

Answer 18

a substance that speeds up the rate of reaction and is left chemically unchanged, so it can be reused

Question 19

how does a catalyst speed up a reaction?

Answer 19

a catalyst provides an alternative pathway for the reaction which has a lower activation energy