1. Revision C3: What the examiner wants

2. Rates of Reaction
How much product is formed or how much reactants are used OVER time.
Read the question.
Write the equation, learn it if you don’t understand it. Mg + 2HCl MgCl2 +H2
If in the exam they ask you to react calcium with HCl balanced simple equation would be: Ca + 2HCl CaCl2 +H2
NOTE: calcium is from the same group as magnesium it needs two chlorines (or two from any element from group seven) to bond with.
Now calculate RATE. Remember, divide how much is used up/made by how long it took.
For this question: 0.2g Magnesium ÷ 120
Now for the units: you divided mass in grams by time in seconds so units for rate are g/s

3. YES Examiners and Teachers are boring, bore us with details PLEASE.
Reaction stops when the graph begins to level off/become horizontal.
How does the catalyst work?
Speeds up the rate of reaction without getting used up.
Reaction will happen faster but will still get the same MAXIMUM amount of product.
Make sure that your is neater than mine.
Catalyst lowers the activation energy needed to make the reaction happen. This means less energy is needed.
YES Examiners and Teachers are boring, bore us with details PLEASE.
Powdered zinc instead of lumps:
This has LARGER surface area. This means more ZINC partials are exposed.
Which will result in more collision between zinc and sulphuric acid. More collision will mean more successful collisions which will result in the formation of the desired product: in this case zinc sulphate

4. Rate of Reaction: Concentration
Rate of reaction can be increase by increasing the concentration.
As the concentration increases the particles become more crowded. This will increase the number of collisions between the reacting particles.
More collision per second means more successful collisions.
This will result in an increased rate of reaction.

5. Rate of Reaction: Temperature
As the temperature increases the particles gain KINETIC ENERGY (move more) and move around more quickly/ more energetic.
Therefore partials will collide more frequently with more energy resulting in more collisions per second and therefore more successful collisions.

6. Rates of Reaction: GAS
Only if the reactants are gases you can increase the pressure.
The reacting particles are squished together. This increases collisions frequency per second which means increased number of successful collisions and therefore increased rate of reaction.

7. Therefore Mr for water = 16 + (2x1) = 18
Relative formula mass, Mr
The relative formula mass (Mr) 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, there’s two of them!!
Therefore Mr for water = 16 + (2x1) = 18

8. Use the Periodic table to calculate Mr.
Find the element in the periodic table.
This is oxygen.
You need the top number.
Add all the numbers together.
This gives you the total Mr for the compound. 16 O 8
NH3
There are 1 nitrogen atom and 3 hydrogen that make up ammonia.
Add the Mr together for all 4 atoms and that give you the molecular mass for ammonia (the Mr )

9. Simple formulae to learn
Covalent formulae
Ionic formulae
H2O
CO2
NH3 H2 O2 N2
SO2
Water
Carbon dioxide
Ammonia
Hydrogen
Oxygen
Nitrogen
Sulphur dioxide
NaCl
CaCl2
MgO
HCl
H2SO4
HNO3
NaOH
Ca(OH)2
CaCO3
Al2O3
Fe2O3
Sodium chloride
Calcium chloride
Magnesium oxide
Hydrochloric acid
Sulphuric acid
Nitric acid
Sodium hydroxide
Calcium hydroxide
Calcium carbonate
Aluminium oxide
Iron oxide

10. Conservation of mass in reactions
In any reaction the total mass of products is the same as the total mass of the reactants
Example 1 – Magnesium oxide and hydrochloric acid Mg O H Cl
1 x magnesium, 1 x oxygen, 2 x hydrogen and 2 x chlorine atoms
Also 1 x magnesium, 1 x oxygen, 2 x hydrogen and 2 x chlorine atoms
Example 2 – Burning methane C H O

11. Product
All symbols are there (except water). All you are asked to do is put them into the equation.
They need to see that you can read and put reactants and products in the correct place. All they expect you to know is the symbol for water.
THESE are the REACTANTAS
This involves no chemistry.
Remember mass of reactants (total of all reactants) is the same as mass of products (total of all products).
So……
Total mass o reactants= 10.3g take away from that the mass of water, this will equal the mass of nitric acid, which they want you to work out. 10.3g-1.8g=8.5g
Read the question and remember the rule.

12. 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 + O MgO
ignore
Reacting ratio
2 Mg
makes
2 MgO
Step 2: WORK OUT the relative formula masses (Mr):
2Mg = 2 x 24 = MgO = 2 x (24+16) = 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

13. Ca(OH)2 + 2HCl CaCl2 + 2H2O 2 HCl 1 CaCl2
2) What mass of hydrochloric acid is needed to produce 11.1g calcium chloride?
Ca(OH)2 + 2HCl CaCl H2O
ignore
ignore
reacting ratio
2 HCl
makes
1 CaCl2
Mr: 2HCl = 2 x ( ) CaCl2 = 40 + (2 x 35.5)
= = 111
111g CaCl2 produced by 73g HCl
1g of CaCl2 produced by (73/111)= 0.66
so 11.1g produced by 0.66 x 11.1 = 7.3g of HCl

14. Percentage yield= actual yield x100 predicted yield
Percentage yield is a way of comparing amount of product made (actual yield) to amount expected (predicted yield)
Percentage yield= actual yield x100
predicted yield
100% yield means...
0% yield means...
we have lost no product
we have lost all the product

15. What are the reasons we might not get the mass we expect?
Not all the reactant made into product
Loss when transferring liquids
Loss when filtering
Loss when evaporating

16. All this is there for information ONLY
All this is there for information ONLY. You don’t need it in the question.
All this is there for information is important. This is what you need to use.
Now use the equation that you must learn.
(0.70÷0.80) x 100%= 87.5%

17. Atom economy
The atom economy of a chemical reaction is a measure of the amount of starting materials that become useful products.
Inefficient, wasteful processes have low atom economies, atoms are wasted not made into useful products. .
Efficient processes have high atom economies, and are important for sustainable development, as they use fewer natural resources and create less waste.
HOW do you know what is a useful product?? READ THE QUESTION

18. Calculating Atom Economy
Atom economy is a way of measuring the amount of atoms that are wasted when manufacturing a chemical
Atom Economy= Mr of desired productx100
Sum of Mr of all products
100% atom economy means...
0% yield means...
all atoms in the reactant have been converted to the desired product
we have lost all the product

19. Exothermic Reactions Magnesium + Hydrochloric acid Magnesium
Gets hot
Heat given out, reactants lose energy.
Hydrochloric acid
Energy level diagram
The reactants start with more energy this is lost to the surroundings as heat during the reaction.
The products have less energy than the reactants.
Reactants
Energy / kJ)
Products
Progress of reaction

20. Heat energy released as a consequence.
Exothermic Reactions
During an exothermic reaction bonds are formed.
It is this process that releases heat energy.
No bond between atoms
High in energy.
Reactants
Energy / kJ)
Products
Atoms now bonded lower in energy
Progress of reaction
Heat energy released as a consequence.

21. Endothermic Reactions
Ammonium nitrate + Water
Ammonium nitrate
Heat taken in, reactants gain energy.
Surroundings get cooler
Gets Cooler
Water
25o C
20o C
Energy level diagram
The reactants start with less energy, they gain energy from the surroundings.
The products have more energy than the reactants.
Products
Energy / kJ)
Reactants
Progress of reaction

22. Endothermic Reactions
During an endothermic reaction bonds are broken.
It is this process that takes in heat energy.
Products
Bonds broken
Energy / kJ)
Reactants
Atoms already bonded.
Progress of reaction
Heat energy taken in as a consequence.

23. What makes a reaction exo- or endothermic?
For a reaction to be overall exothermic more bonds have to be formed than broken.
For a reaction to be endothermic more bonds have to broken than formed.
To Do:
Draw and annotate an energy level diagram showing bond making/breaking for the endothermic reaction:
In summary

24. Formulae: Learn how to use these.
E=mc∆T
Energy supplied (J)
Specific heat capacity of water (J/g/oC)
Rise in temperature (oC)
Mass of water (g)
This is: 4.2 J/g/oC
Energy supplied (J)
Fuel Efficiency (J/g)
Mass of fuel burnt (g)

25. Comparing Energy from Fuels
Constants (to make the experiment a fair test):
Same volume of water
Same calorimeter
Same heating time
Remember the practical that we did in class?? The oil burner, learn how it works, learn to draw it. Learn how to make it a fair test.
That we measured mass of fuel to find out how efficient they are. If you get stuck find it on BBC bite size.

26. Propanol give out the most energy
Propanol give out the most energy. We know this because it has the biggest energy change.
You need to draw something like this. And list the 3 things we do to keep it a fair test. And why we measure the mass of fuel before and after.
Learn the experiment and how we test for energy output/fuel that gives most energy.

27. Temp before heating in C Temp after heating in C
Which cooking fuel is best?
Fuel
Temp before heating in C
Temp after heating in C
Temp change in C
Rank order
methane 20 76
camping gas 21 73
cheap oil 19 64
expensive oil 66
Calculate the temperature change of a beaker of water for the same amount of each fuel. Then decide which fuel is best.

28. Energy transferred (J)
Running an airline
These are the results presented to an airline after a test of four fuels. Calculate the energy given off per gram of fuel for each Which do you think is the ‘best’ fuel?
Fuel
Temp before (C)
Temp difference (C)
Energy transferred (J)
Mass of fuel used (g)
Energy per gram (J/g) A 20 56
3.2 B 21 64
4.3 C 19 52
3.6 D 61
3.9

29. Batch process
Reactants put in one end and product removed at the other end;
Make a product on demand and on a small scale. Fixed amount.
Can be used to make a variety of products. As an when needed and easy to store until needed.
Good for making drugs that have sell buy date.
Easy to change the product from one to another.
Very labour intensive- reactor needs to be filled emptied and cleaned.
Due to fact that it is labour intensive it will have high cost per tonne.
Time needed for cleaning and t change product line
Disadvantage
Disadvantage
Disadvantage
This process is used when new pharmaceuticals (drugs) are produced.

30. Continuous process
A continuous process is one in which reactants are fed in one end and a constant stream exists form the other;
It runs 24 hours a day and is only shut down for maintenance of equipment or deep clean.
Only used in well known and understood reactions. Eg the Haber process.
High level of automation so few staff are required, making it cheaper per tonne of product.
Takes less energy to maintain, as long as the process can be kept running.
Disadvantages:
High building set up cost for the chemical plant or factory.
The sufficient if not used constantly.

31. Ideas for new drugs come from a variety of places;
Extracted from plants and other natural products (crushed to disrupt and break the cell wall to release the desired product, boil in a suitable solvent to dissolve compound, chromatography to separate and identify individual compounds)
Subtly change old drugs- sometimes this is what scientist do instead of making new drug.
Depending on the question, you might have to say that a mixture needs (after dissolving) filtering, evaporating, distillation to separate mixtures. Learn these if you are unsure.
Read the question: answer underlined.
How does chromatography enable scientist to check for purity: because they can check for the presence of other substances, chromatography allows for separation so we can visually see different compounds in the gel.

32. Why are drugs so expensive?
research and testing;
labour costs;
energy costs;
raw materials;
time taken for development;
marketing.
often more labour intensive;
less automation possible;
research and testing may take many years; cost money
raw materials likely to be rare and/or involve expensive extraction from plants;
legislative demands.
research and development time and associated labour costs;
time required to meet legal requirements including timescale for testing and human trials;
anticipated demand for new product ;
length of pay back time for initial investment.

33. TESTING scientist need: labour/salaries/wages/cost of workers.
electricity/energy/gas/power costs.
Time taken to complete process.
Equipment cost
Health and safety issues with the drug
Pollution controls.
Rent, water rates all cost money.
The question mentions two factors that are both expensive and TIME consuming.
Learn all of these in case it comes up as a 6 mark question.

34. Humans and animals are very different, testing on animals might give different results than testing on humans.
Testing on humans risk human harm.
No many human volunteers.
Rights of humans is more important than rights of animals.

35. This means say to reasons why batch is better than continues to make medicines:
Drugs are needed in small amount
Made in small scale, this means they can switch from making on type of drug to another.
Advantage of this:
Bath can be called back easily if there is a problem with it.
Disadvantage:
Labour intensive…… and so on, look at pervious notes.

36. Used the above equation. LEARN it. (0.6/0.8) x 100% = 75%
To answer the last question look at what Alex did.
He measured and transferred liquids.
He heated, and evaporated.
THEREFORE: he didn’t get 100% yield because he might have lost some reactants or products during any of the above processes.
LEARN THESE. They might come up.

37. 6 marks question on drugs

38. Answers:
NOTE: Scientist publish findings about new drugs to allow other scientist to test their findings and see if they get the same results. To allow doctors and pharmacists know about the drug. To show that their drug is safe.
To give scientist chance to develop it further.

39. Allotropes
Different forms of the same element in the same physical state. Meaning all forms are solid in this case but the atoms are BONDED differently.
Carbon has the allotropes;
Diamond
Graphite
Buckminsterfullerene

40. Properties of graphite and diamond
Write a list of all the properties you can think of for diamond and graphite.
Diamond
Graphite
Black and opaque
Soft and slippery
High melting point
Conducts electricity
Lustrous
Colourless and transparent
Very hard
Very high melting point
Does not conduct electricity
Lustrous with a brilliant shine
They are both made of only carbon, why do they have such different properties
LEARN THE STRUCTURE of both: WHAT THEY LOOK LIKE (see next two slides)

41. Graphite The carbon atoms are arranged in layers.
Within each layer there are strong covalent bonds. (meaning high melting point).
Between layers there are much weaker forces (meaning they are soft and slippery). These force are easy to break and allow you to write with a pencil.
Between the layers the electron are delocalised (it is able to conduct electricity)
Electrons move freely (delocalised) which means they can carry a charge. Making graphite a good conductor.

42. Diamond
Each carbon atom is held in place by four strong covalent bonds.
These bonds require large amounts of energy to break. The means diamond has a high melting points and hardness.
No free electrons so cannot conduct electricity.
Last thing- be positive, smile and you can take on the world. Any time you need help come find me or me. I will get back to you. Make me proud  I believe in all of you.