23/03/2016
OCR Additional Science
Chemical Economics
W Richards
The Weald School
Rates of Reaction
23/03/2016
Oh no! Here comes
another one and it’s
got more energy…
Here comes another
one. Look at how slow
it’s going…
It missed!
Here comes an acid particle…
No effect! It didn’t
have enough energy!
Hi. I’m Mike Marble. I’m
about to have some acid
poured onto me. Let’s see
what happens…
Rates of Reaction
23/03/2016
Chemical reactions occur when different
atoms or molecules _____ with enough
energy (the “________ Energy):
View animation
Basically, the more collisions we get the _______ the reaction goes.
The rate at which the reaction happens depends on four things:
1) The _______ of the reactants,
2) Their concentration/pressure
3) Their surface area
4) Whether or not a _______ is used (catalysts are specific to
certain reactions)
Words – activation, quicker, catalyst, temperature, collide
Measuring the Rate of Reaction
23/03/2016
Two common methods:
Rate of reaction graph
Amount of
product
formed/
reactant
used up
Fast rate
of reaction
here
23/03/2016
Slower rate of reaction here
due to reactants being used up
Slower reaction
Time
Rate of reaction graph
23/03/2016
Q. What if less reactants were used?
Amount of
product
formed/
reactant
used up
Time
Calculating the Rate of Reaction
23/03/2016
Rate of reaction = the gradient of the graph
20cm3
Amount of
product
formed/
reactant
used up
Rate of reaction = 2cm3/s
10s
Time
Atomic mass
23/03/2016
RELATIVE ATOMIC MASS, Ar
(“Mass number”) = number of
protons + number of neutrons
SYMBOL
PROTON NUMBER = number of
protons (obviously)
Relative formula mass, Mr
23/03/2016
The relative formula mass of a compound is the relative atomic
masses of all the elements in the compound added together.
E.g. water H2O:
Relative atomic mass of O = 16
Relative atomic mass of H = 1
Therefore Mr for water = 16 + (2x1) = 18
Work out Mr for the following compounds:
1) HCl
H=1, Cl=35 so Mr = 36
2) NaOH
Na=23, O=16, H=1 so Mr = 40
3) MgCl2
Mg=24, Cl=35 so Mr = 24+(2x35) = 94
4) H2SO4
H=1, S=32, O=16 so Mr = (2x1)+32+(4x16) = 98
5) K2CO3
K=39, C=12, O=16 so Mr = (2x39)+12+(3x16) = 138
23/03/2016
Calculating the mass of a product
E.g. what mass of magnesium oxide is produced when 60g of
magnesium is burned in air?
Step 1: READ the equation:
2Mg + O2
2MgO
IGNORE the
oxygen in step 2 –
the question
doesn’t ask for it
Step 2: WORK OUT the relative formula masses (Mr):
2Mg = 2 x 24 = 48
2MgO = 2 x (24+16) = 80
Step 3: LEARN and APPLY the following 3 points:
1) 48g of Mg makes 80g of MgO
2) 1g of Mg makes 80/48 = 1.66g of MgO
3) 60g of Mg makes 1.66 x 60 = 100g of MgO
1) When water is electrolysed it breaks down into hydrogen and23/03/2016
oxygen:
2H2O
2H2 + O2
What mass of hydrogen is produced by the electrolysis of 6g of water?
Work out Mr: 2H2O = 2 x ((2x1)+16) = 36
2H2 = 2x2 = 4
1.
36g of water produces 4g of hydrogen
2. So 1g of water produces 4/36 = 0.11g of hydrogen
3. 6g of water will produce (4/36) x 6 = 0.66g of hydrogen
2) What mass of calcium oxide is produced when 10g of calcium burns?
2Ca + O2
Mr: 2Ca = 2x40 = 80
2CaO
2CaO = 2 x (40+16) = 112
80g produces 112g so 10g produces (112/80) x 10 = 14g of CaO
3) What mass of aluminium is produced from 100g of aluminium oxide?
2Al2O3
4Al + 3O2
Mr: 2Al2O3 = 2x((2x27)+(3x16)) = 204
4Al = 4x27 = 108
204g produces 108g so 100g produces (108/204) x 100 = 52.9g of Al2O3
Percentage Yield
23/03/2016
Theoretical yield = the amount of product that should be made
as calculated from the masses of atoms
Actual yield = what was actually produced in a reaction
Percentage yield
=
actual yield (in g)
theoretical yield
Example question:
65g of zinc reacts with 73g of hydrochloric acid and
produces 102g of zinc chloride. What is the percentage
yield?
Zn + 2HCl
ZnCl2 + H2
Percentage yield
Percentage yield =
Actual yield
Predicted yield
23/03/2016
X 100%
Some example questions:
1) The predicted yield of an experiment to make salt was 10g.
If 7g was made what is the percentage yield?
2) Dave is trying to make water. If he predicts to make 15g
but only makes 2g what is the percentage yield?
3) Sarah performs an experiment and has a percentage yield
of 30%. If she made 50g what was she predicted to make?
Batch and Continuous processes
23/03/2016
In summary:
Process
Batch
Continuous
What it means
Reactants are thrown
in, the reaction
happens and the batch
is removed
The reactants are
continually fed in and the
products are continually
removed (e.g. the Haber
Process)
Advantages
Makes a wide variety
Operate all the time and
of products on demand automatically, makes a large
amount of product
Disadvantages
More labour intensive
Can only make one product
Developing new medicines
23/03/2016
The process:
Step 1 - research
Step 2 - development
Step 3 - legalities
Step 4 - manufacture
Step 5 - marketing
Forms of Carbon
23/03/2016
1) Diamond – very hard, doesn’t conduct
electricity, very high melting point
2) Graphite – soft, does conduct
electricity, very high melting point
3) Buckminsterfullerene – 60 carbon
atoms arranged in a sphere
Forms of Carbon
23/03/2016
Choose a form of carbon and research the following:
1) What properties does this form of carbon have?
2) How are the electrons arranged in this structure?
3) How does the structure of this form affect its properties?
Nanoscience
23/03/2016
Nanoscience is a new branch of science that refers to
structures built from a few hundred atoms and are 1100nm big. They show different properties to the same
materials in bulk. They also have a large surface area to
volume ratio and their properties could lead to new
developments in computers, building materials etc.
Task: research nanoscience
and find two current and/or
future applications of this
science.
Using sea water
23/03/2016
Research task:
Q. Given all the problems with water shortages, why can’t
we just purify sea water and use it for drinking water?