Chapter 5 - kinetics

Question 1

define collision theory

Answer 1

the idea that for a reaction to take place, particles must collide with the required energy or more, and with the right orientations
more collisions will result in a greater rate of reaction

Question 2

what factors affect the rate of reaction

Answer 2

catalysts
temperature
concentration (liquids)
pressure (gases)
surface area (solids)

Question 3

define activation energy

Answer 3

the minimum energy required for a particle to start breaking bonds
the minimum energy for a reaction to take place

Question 4

what is a transition state

Answer 4

the species that exist on the peak of a curve on an enthalpy diagram
at this point, some bonds are made and some are being broken

Question 5

describe the motion of particles in any gas or solution

Answer 5

particles all move with different speeds, however their average speed depends on the temperature of the solution

Question 6

what are the axis of a maxwell boltzmann distribution graph

Answer 6

the y axis is the fraction of particles with energy E
the x axis is the energy E

Question 7

what can be concluded from a maxwell boltzmann distribution graph

Answer 7

no particles have zero energy
most have intermediate energies ( the peak of the cureve)
few particles have high energies
the energy a particle can have has no upper limit

Question 8

what can be concluded from marking the Ea on a maxwell boltzmann distribution graph

Answer 8

the number of particles with or more than the required Ea to react
this shows the proportion of particles that will react when the activation energy is supplied

Question 9

how does temperature change the appearance of a maxwell boltzmann distribution graph

Answer 9

at higher temps, the peak is lower and moves to the right

Question 10

how will using a catalyst look like on an enthalpy diagram and on a maxwell boltzmann distribution graph

Answer 10

the peak (the transition state) will be lower on an enthalpy diagram, however the overall energy change will not change
the line showing Ea will be more to the left, hence the area beneath the graph to the right of the Ea will be greater and a greater proportion of particles will be able to successfully collide

Question 10

what changes about the energy of the particles when the temperature is higher

Answer 10

a higher proportion of particles have the required Ea to react
this is the reason for why increasing the temp will increase the rate of reaction

Question 10

what is a catalyst

Answer 10

a substance which increaces the rate of reaction without being chemically changed or used up

Question 11

how do catalysts work

Answer 11

they provide an alternate reaction pathway which requires less activation energy

Question 12

what catalyst is used in the haber process

Answer 12

iron

Question 13

what catalyst is used in making nitric acid

Answer 13

platinum and rhodium

Question 13

what catalyst is used in hardening of fats with hydrogen

Answer 13

nickel

Question 14

what catalyst is used in cracking hydrocarbon chains from crude oil

Answer 14

aluminium oxide and silicon dioxide zeolite

Question 15

what catalyst is used in catalytic converters in cars

Answer 15

platinum and rhodium

Question 16

what catalyst is used in esterification

Answer 16

H^+ ions

Question 17

how do catalytic converters work

Answer 17

in adsorption, the gases bond to the metal atoms which hold the molecule sin the right positions to react together.
then after reacting the products break away from the metals in desorption

Question 18

what is a zeolite

Answer 18

a mineral which has an open pore structure so that it can trap singular molecules in small spaces which can change their structure and reactivity

Question 19

how are fats hardeened

Answer 19

nickel is added to unsaturated fats then hydrogen is bubbled through the fat which hardens it to the desire of the manufacturer
the nickel is then filtered off

Question 20

why are CFCs harmful

Answer 20

they are harmful to the ozone layer because they are unreactive and stay in the atmosphere for a long time until they decompose into chlorine atoms
chlorine acts as a catalyst in the breaking down of O3 molecules - ozone

Question 21

what does the ozone layer do, why is it important

Answer 21

it acts as a sheild which prevents the suns UV rays from heating the earths surface too much
in essence it makes the earth habitable