OCR Additional Science

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OCR Additional Science
Chemical Economics
W Richards The Weald School
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Acids and Bases
The pH scale is a way of showing how strong or
weak an acid or base is
Stomach acid
Lemon juice
Water
Soap
Oven cleaner
Baking powder
An alkali is simply a base that has been
dissolved.
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Common acids and alkalis
Acids
Alkalis
Hydrochloric acid, HCl
Sodium hydroxide, NaOH
Nitric acid, HNO3
Potassium hydroxide, KOH
Sulphuric acid, H2SO4
Magnesium hydroxide, Mg(OH)2
Calcium hydroxide, Ca(OH)2
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Neutralisation reactions
When acids and alkalis react together they will
NEUTRALISE each other
Sodium hydroxide
Hydrochloric acid
OH
Cl
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Acids and Carbonates
General equation
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Neutralisation experiment
For example, in a neutralisation experiment we
can mix sodium hydroxide (an _____) and
hydrochloric acid together and they will ________
each other. The equation for this reaction is

• A ____ was formed during the reaction, and we
  could have separated this by __________ the
  solution. The salt that we formed depended on
  the acid
• Hydrochloric acid will make a CHLORIDE
• Nitric acid will make a _________
• Sulphuric acid will make a _________

Words nitrate, neutralise, alkali, sulphate,
salt, evaporating
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Neutralisation reactions
The basic equation for any neutralisation
reaction is
Write word and chemical equations for the
following reactions

1. Hydrochloric acid sodium hydroxide
2. Hydrochloric acid potassium hydroxide
3. Nitric acid potassium hydroxide
4. Sulphuric acid calcium hydroxide
5. Nitric acid copper oxide, CuO
6. Sulphuric acid calcium carbonate, Ca(CO)3

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Making salts
Whenever an acid and alkali neutralise each other
we are left with a salt, like a chloride or a
sulphate. Complete the following table
Hydrochloric acid Sulphuric acid Nitric acid
Sodium hydroxide Sodium chloride water
Potassium hydroxide Potassium sulphate water
Calcium hydroxide Calcium nitrate water
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Sulphuric acid
Cleaning metals
Car batteries
Uses of sulphuric acid
Neutralising fertilisers
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Atomic mass
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Relative formula mass, Mr
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
Therefore Mr for water 16 (2x1) 18
Work out Mr for the following compounds

1. HCl
2. NaOH
3. MgCl2
4. H2SO4
5. K2CO3

H1, Cl35 so Mr 36 Na23, O16, H1 so Mr
40 Mg24, Cl35 so Mr 24(2x35) 94 H1, S32,
O16 so Mr (2x1)32(4x16) 98 K39, C12,
O16 so Mr (2x39)12(3x16) 138
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Calculating the mass of a product
E.g. what mass of magnesium oxide is produced
when 60g of magnesium is burned in air?
Step 2 WORK OUT the relative formula masses
(Mr) 2Mg 2 x 24 48 2MgO 2 x
(2416) 80

• Step 3 LEARN and APPLY the following 3 points
• 48g of Mg makes 80g of MgO
• 1g of Mg makes 80/48 1.66g of MgO
• 60g of Mg makes 1.66 x 60 100g of MgO

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• Work out Mr 2H2O 2 x ((2x1)16) 36
  2H2 2x2 4
• 36g of water produces 4g of hydrogen
• So 1g of water produces 4/36 0.11g of hydrogen
• 6g of water will produce (4/36) x 6 0.66g of
  hydrogen

Mr 2Ca 2x40 80
2CaO 2 x (4016) 112 80g produces 112g so
10g produces (112/80) x 10 14g of CaO
Mr 2Al2O3 2x((2x27)(3x16)) 204 4Al
4x27 108 204g produces 108g so 100g produces
(108/204) x 100 52.9g of Al2O3
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Another method
Try using this equation
Mass of product IN GRAMMES
4
6g
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So mass of product (4/36) x 6g 0.66g of
hydrogen
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Percentage Yield
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
Example question
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Percentage yield

• Some example questions
• The predicted yield of an experiment to make salt
  was 10g. If 7g was made what is the percentage
  yield?
• Dave is trying to make water. If he predicts to
  make 15g but only makes 2g what is the percentage
  yield?
• Sarah performs an experiment and has a percentage
  yield of 30. If she made 50g what was she
  predicted to make?

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Fertilisers

• Fertilisers are chemicals used to help plants to
  grow. They contain three main elements
• Nitrogen
• Phosphorus
• Potassium

Fertiliser Chemicals used to make it
Ammonium sulphate Ammonia and sulphuric acid
Ammonium nitrate
Ammonium phosphate
Potassium nitrate
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Eutrophication
Eutrophication is when lakes become stagnant due
to careless use of fertiliser. There are six
steps
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Eutrophication
Cantbreathe
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Eutrophication
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Calculating percentage mass
Calculate the percentage mass of magnesium in
magnesium oxide, MgO
Ar for magnesium 24 Ar for oxygen 16 Mr for
magnesium oxide 24 16 40 Therefore
percentage mass 24/40 x 100 60

• Calculate the percentage mass of the following
• Hydrogen in hydrochloric acid, HCl
• Potassium in potassium chloride, KCl
• Calcium in calcium chloride, CaCl2
• Oxygen in water, H2O

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Reversible Reactions
Some chemical reactions are reversible. In other
words, they can go in either direction
If a reaction is EXOTHERMIC in one direction what
must it be in the opposite direction?
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Reversible Reactions
When a reversible reaction occurs in a CLOSED
SYSTEM (i.e. no reactants are added or taken
away) an EQUILIBRIUM is achieved in other
words, the reaction goes at the same rate in both
directions
More products
Less products
Less products
More products
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Making Ammonia
Guten Tag. My name is Fritz Haber and I won the
Nobel Prize for chemistry. I am going to tell
you how to use a reversible reaction to produce
ammonia, a very important chemical. This is
called the Haber Process.
To produce ammonia from nitrogen and hydrogen you
have to use three conditions

• High pressure
• 450O C
• Iron catalyst

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Haber Process The economics
A while ago we looked at reversible reactions

• 1) If temperature was DECREASED the amount of
  ammonia formed would __________...
• However, if temperature was INCREASED the rate of
  reaction in both directions would ________
  causing the ammonia to form faster
• If pressure was INCREASED the amount of ammonia
  formed would INCREASE because there are less
  molecules on the right hand side of the equation

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The Haber Process Economics
How quickly ammonia is made
The cost of electricity/gas
Cost of reactants
The cost of wages
Factors affecting the cost of making ammonia
Cost of equipment
Catalyst
Temperature
Pressure
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Haber Process Summary
A low temperature increases the yield of ammonia
but is too slow A high temperature improves the
rate of reaction but decreases the yield too
much A high pressure increases the yield of
ammonia but costs a lot of money
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Washing Powder

• Washing powder is a mixture and made mainly of
• Detergent (the bit that does the cleaning)
• Bleach (to remove stains)
• Water softener to soften hard water
• Brightener to whiten whites
• Enzymes to digest food stains

Name the symbol
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Washing up liquid

• Washing up liquid is a mixture as well and
  contains
• Detergent
• Water (to dissolve and dilute the detergent)
• Water softener
• Rinse agent to help the water run off
• Colour and fragrance

The detergent in washing up liquid is often a
salt and made from the basic equation
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The structure of a detergent
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How detergents work
Step 1 The hydrophobic end of the detergent
molecule is repelled by water, causing it to
stick to the oil droplet.
Step 2 As more and more detergent molecules are
absorbed the oil is lifted off the plate
Oil
Step 3 When it is totally surrounded the oil is
washed away
Plate
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Batch and Continuous processes
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 of products on demand Operate all the time and automatically, makes a large amount of product
Disadvantages More labour intensive Can only make one product
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Developing new medicines
The process
Step 1 - research
Step 2 - development
Step 3 - legalities
Step 4 - manufacture
Step 5 - marketing
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Forms of Carbon
1) Diamond very hard, doesnt 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
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Forms of Carbon
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?

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Nanoscience
Nanoscience is a new branch of science that
refers to structures built from a few hundred
atoms and are 1-100nm 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.
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Water

• Amazing facts about water
• 95 of your body mass is water (94 in women due
  to a higher body fat content)
• Dinosaurs would have drunk the same water you do
• Water dissolves more substances than any other
  liquid
• Around 75 of the worlds surface is made of
  water
• To feel thirsty you need to lose around 1 of
  your body water
• 5,000 children die every day due to not having
  clean drinking water
• An average person in the West uses 200-300 litres
  of water every day

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Water
Our drinking water comes from four main sources
rivers, lakes, reservoirs and aquifiers (wells
etc). To be used as drinking water it has to be
treated
The Water Treatment Process
1) Sedimentation
2) Filtration
3) Chlorination
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Pollutants in water

• Water may contain pollutants from sources such
  as
• Old lead pipes
• Fertiliser run off
• Insecticides etc

Allowed concentrations
Pollutant Maximum amount allowed
Nitrates 50 parts per billion
Lead 50 parts per billion
Pesticides 0.5 parts per billion
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Dissolved ions
The dissolved ions of some salts are easy to
identify as they will undergo precipitation
reactions, i.e. they will make a solid when
mixed with the right substance.
For each of the following reactions describe what
happened, the colour of the precipitate that was
formed and write a chemical reaction

1. Sodium sulphate barium chloride
2. Sodium chloride silver nitrate
3. Sodium bromide silver nitrate
4. Sodium iodide silver nitrate

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Using sea water
Research task
Q. Given all the problems with water shortages,
why cant we just purify sea water and use it for
drinking water?