Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Title: Rates of Chemical Reactions
Description: Diffusion Osmosis Understanding Rate Curve Factors affecting rates ( Catalyst, Temperature, Concentration, Surface Area) Cooling Curve explained Heating curve Explained Types of Catalyst
Description: Diffusion Osmosis Understanding Rate Curve Factors affecting rates ( Catalyst, Temperature, Concentration, Surface Area) Cooling Curve explained Heating curve Explained Types of Catalyst
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Stephen Carridice
RATES OF CHEMICAL REACTIONS
RATES OF CHEMICAL REACTIONS
Some chemical reaction occurs instaneously,
think of the speed of an explosion, Others
weathering of rocks, occurs extremely slow,
Ripening of fruits, fire works
...
We can
therefore measure the rate of a reaction by
monitoring changes in the concentration of
reactants or products
RATES OF CHEMICAL REACTIONS
The rate of a reaction is the change in
concentration of reactants or products in unit
time
...
RATES OF CHEMICAL REACTIONS
Calculating the rate of a reaction:
Consider the reaction between solid carbonate
and hydrochloric acid
...
The volume of gas produce
as a reaction proceeds can be used to measure
the rate of the reaction
...
97cm3s-1
What the rate between 20s and 40 s?
RATES OF CHEMICAL REACTIONS
Volume of carbon dioxide(Cm3)
400
Ensure it touches
the curve line
350
300
250
Volume of gas (cm3) 200
Volume of carbon dioxide(Cm3)
150
100
50
0
0
20
40
60
Time(s)
80
100
120
RATES OF CHEMICAL REACTIONS
Points R1: 300cm3 at 40s
R2: 200cm3 at 20s
Rate=Change in the concentration of CO2/ time
taken for change
Rate =(300-200)cm3/40-20s=5cm3s-1
RATES OF CHEMICAL REACTIONS
Each of these rates is really the average rate
during the specific time interval
...
The
steepness of the curve indicates the rate of
reaction
...
The reaction is fastest at the beginning
and where the curves flatten no more gas is
produced
...
To do this
you would draw a tangent to the line of the
curve at the 20 second point
...
4cm3s-1
RATES OF CHEMICAL REACTIONS
Use the graph to determine:
1
...
The rate at 50s and 80s
3
...
Answers
50s=2
...
57cm3s-1
First 40 seconds:7
...
3 conditions are necessary
1
...
Reactant molecules, on collision, must have
energy equal to or greater than the necessary ‘
activation energy ( is the minimum energy
required for bonds within reactant molecules to
break and for particles to become sufficiently
energized for products to formed)
RATES OF CHEMICAL REACTIONS
3
...
Collision theory
This states that there must be effective collisions in
order for chemical reactions to take place
...
They require that all the reactants are
correctly oriented and have the required
activation energy
RATES OF CHEMICAL REACTIONS
Effective collision
wrong orientation, suffient energy
Effective collision- Correct orientation, Sufficient Energy
Energy
Activation energy
v
v
Product
wrong orientation, insuffient energy
Correct orientation, insuffient energy
Reaction path way
RATES OF CHEMICAL REACTIONS
Factors which affect the rates of chemical
reactions
Concentration( or pressure for gaseous system)
Temperature
Catalysts
Particle size/ surface area
Light, for some reaction
RATES OF CHEMICAL REACTIONS
The effect of concentration on the rates of
reactions
Theory here is that an increase in
concentration means there are more reactant
molecule in a given volume
...
RATES OF CHEMICAL REACTIONS
Increase the concentration of reactants, more reactant molecules
in a given volume is able to collide to speed up the reaction
RATES OF CHEMICAL REACTIONS
Hydrogen gas produce as result of Mg+HCL RXN by
varying the concentration of HCL
A=2
...
0MHCL
B=0
...
0M has the steepest initial gradient and curve C 0
...
The
rxn rate is fastest with 2M HCL
RATES OF CHEMICAL REACTIONS
The same effect is true for pressure
...
The volume of a gas decrease as the pressure
increase
RATES OF CHEMICAL REACTIONS
The effect of temperature on reaction rates
The rate of a chemical reaction increases as the
temperature of the reactants increases
...
Particles move faster as their temperature
increases
2
...
The collisions are more effective since more
particles have energy equal to or more than the
activation energy
...
A catalyst do not appear in the chemical
equation
...
RATES OF CHEMICAL REACTIONS
The effect of catalyst on reaction rates
Energy
A) uncatalyzed
b) catalyzed
reactants
Activation energy
Reaction pathway
Catalyst lowers the activation energy
RATES OF CHEMICAL REACTIONS
The effect of Catalyst on reaction rates
Catalyst provide different or easier way to form products
...
Catalyst may bring reacting molecule closer togetherthus more opportunities for reactant molecules to
collide
...
MnO2
CuO
ZnO
MnO2 has the fastest rate of rxn while ZnO has the slowestrxn rate
RATES OF CHEMICAL REACTIONS
The effect of Surface Area on reaction rates
It follows that the smaller the particles of the solid
are, the greater the surface area available for
collisions, and the greater the reaction rate
...
A
strip of heated iron wire is not affected when
placed in a jar of oxygen
...
RATES OF CHEMICAL REACTIONS
The effect of catalyst on reaction rates
The action of teeth helps to increase the
surface area of food
...
Thus leads to more effective
digestion by biological catalyst-enzymes
Title: Rates of Chemical Reactions
Description: Diffusion Osmosis Understanding Rate Curve Factors affecting rates ( Catalyst, Temperature, Concentration, Surface Area) Cooling Curve explained Heating curve Explained Types of Catalyst
Description: Diffusion Osmosis Understanding Rate Curve Factors affecting rates ( Catalyst, Temperature, Concentration, Surface Area) Cooling Curve explained Heating curve Explained Types of Catalyst