Chemical synthesis involves chemical reactions to produce desired products from starting reagents. It provides important products like food additives, fertilizers, dyes, paints, and pharmaceuticals. Chemicals can be fine chemicals made in small quantities for uses like flavors or drugs, or bulk chemicals made in large cheap quantities for other chemical processes. Controlled chemical synthesis requires planning reactions, risk assessment, calculating quantities, purification, and yield measurement. Reaction rates depend on factors like particle size, concentration, and temperature.

1. Revision of C6 Chemical synthesisRevision of C6 Chemical synthesis

2. Chemical synthesis: chemical reactions and
processes used to get a desired product using
starting materials called reagents.
The products can be useful for a variety of
purposes but tend to be either…
C6.1 Chemicals are why we need themC6.1 Chemicals are why we need them

3. Understand the importance of chemical synthesis to provideUnderstand the importance of chemical synthesis to provide
food additives, fertilisers,food additives, fertilisers, dyestuffs, paints, pigments and, paints, pigments and
pharmaceuticals.pharmaceuticals.

4. • fine chemicals
A chemical product that is made in relatively small
quantities and is typically high in cost, e.g. a flavouring or
vitamin, drugs etc. They are made to high levels of
purity. Usually in laboratories.
• bulk chemicals
A chemical product that is made in large amounts, very
cheaply and often used to make other chemicals or to
process other materials e.g. bleach, solvents, sulphuric
acid etc. Usually made in industries.
Interpret information about the sectors, scale and
importance of chemical synthesis in industry and
laboratory.

5. Recall the formulae of ….
Gases:
chlorine = Cl2, hydrogen = H2, nitrogen= N2, oxygen = O2
Acids:
hydrochloric acid = HCl, nitric acid = HNO3,
sulfuric acid = H2SO4,
Alkalis
•sodium hydroxide = NaOH,
•magnesium hydroxide Mg(OH)2

6. Salts
[MX] sodium chloride = NaCl,
magnesium oxide = MgO,
potassium chloride = KCl
[MX2]calcium chloride = CaCl2,
More complex salts… magnesium carbonate = [MgCO3]
magnesium sulfate = [MgSO4]; sodium carbonate
[Na2CO3]; calcium carbonate [CaCO3]

7. H ONLY : Work out the formulae of ionic compounds
given the charges on the ions.
Compound Positive ion Negative ion Formula
Sodium
chloride
Na+
Cl-
NaCl
Magnesium
chloride
Mg2+
Cl-
MgCl2
Calcium oxide Ca2+
O2-
CaO
Aluminium
oxide
Al3+
O2-
Al2O3
Magnesium
sulfate
Mg2+
SO4
2-
MgSO4

8. • If magnesium forms Mg2+
ions and sulfate
forms SO4
2-
ions then identify the charges
on the other ions in the following
compounds…
– MgO
– MgCl2
– MgNO3
– Na2SO4
– Al2(SO4)3
– CaSO4
H ONLY Work out the charge on one ion, given the formula
of a salt and the charge on the other ion.

9. harmful /
irritant
corrosive toxic
highly flammable oxidising
Recall the main hazard symbols, and understand the
safety precautions to use when handling hazardous
chemicals.

10. Recall examples of pure acidic compounds which are solid,
liquids and gases.
Solids = citric acid & tartaric acid
Liquids = sulfuric, nitric and ethanoic acids
Gases = hydrogen chloride

11. Recall common alkalis…
 sodium hydroxide
 potassium hydroxide
 calcium hydroxide.

12. Recall the pH scale
pH 1 to pH 3 shows that there is a STRONG ACID
pH 4 to pH 6 shows that there is a WEAK ACID
pH 7 shows that the substance is NEUTRAL
pH 8 to pH 10 shows that there is a WEAK ALKALI
pH 11 to pH 14 shows that there is a STRONG ALKALI

13. Recall the use of indicators and pH meters to measure
pH.
Indicator Colour in
acid
Colour
in
neutral
Colour in
alkali
litmus Red Blue
phenolphthalein colourless pink pink
Universal (a
mixture of
indicators)
Red Green Purple

14. A pH meter.

15. Recall the reactions of acids that produce salts.
Salts can be produced by reacting acids with…..
 metals
 metal oxides
 metal hydroxides
 metal carbonates
Write balanced equations with state symbols to
describe the characteristic reactions of acids

16. Metal + acid
Metal + acid metal salt + hydrogen
calcium + sulfuric
magnesium + hydrochloric
acid
acid
calcium
sulfate
+ hydrogen
magnesium
chloride
+ hydrogen
Ca(s) + H2SO4(aq) CaSO4(aq) + H2(g)
Mg(s) + HCl(aq) MgCl2(aq) + H2(g)

17. Metal oxide + acid
metal + acid metal salt + water
copper + sulfuric
magnesium + hydrochloric
oxide acid
oxide acid
oxide
copper
sulfate
+ water
magnesium
chloride
+ water
CuO(s) + H2SO4(aq) CuSO4(aq) + H2O(l)
MgO(s) 2HCl(aq)+ MgCl2(aq) + H2O(l)

18. Metal hydroxide + acid
metal + acid metal salt + water
potassium + sulfuric
sodium + hydrochloric
hydroxide acid
hydroxide acid
hydroxide
potassium
sulfate
+ water
sodium
chloride
+ water
2KOH(aq) + H2SO4(aq)
NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)
K2SO4(aq) + 2H2O(l)

19. Metal carbonate + acid
metal + acid metal salt + carbon +
water
copper + sulfuric
magnesium +hydrochloric
carbonate acid
carbonate acid
carbonate dioxide
copper + carbon + water
magnesium + carbon + water
sulfate dioxide
dioxidechloride
CuCO3(s) + H2SO4 (aq) CuSO4(aq) + CO2(g) + H2O(l)
MgCO3(s) + 2HCl (aq) MgCl2(aq) + CO2(g) + H2O(l)

20. Recall that the reaction of acid with an alkali to form a
salt is a neutralisation reaction.
Explain what happens during a neutralisation reaction.
• When the number of H+
ions is exactly matched by
the number of OH-
ions to form a pH of 7
• H+
(aq) + OH-
(aq) H2O(l)
• An alkali can cancel out an acid to form a salt and the
water (shown above)
H+
ions from the acid react with OH-
ions from the
alkali.

21. Acidic
substances
…
• Dissolve in water to form H+
ions giving a pH
of less than 7
• Can be…
– solids e.g. citric acid, tartaric acid
– Liquids e.g. sulfuric acid, nitric acid, ethanoic acid
– Gases e.g. hydrogen chloride
• Form salts with many other substances such
as alkalis, hydroxides, carbonates, oxides,
metals

22. Explain that acidic compounds….
Dissolve in water to produce aqueous hydrogen ions H+
(aq)
All acids contain hydrogen – HCl, H2SO4, CH3COOH
Explain that alkaline compounds….
Dissolve in water to produce aqueous hydroxide ions
OH-
(aq)
Form solutions with pH lower than 7.
Form solutions with pH higher than 7.

23. Write down the formula of the salt produced given the
formula of the acid and the alkali.
acid alkali salt
HCl NaOH NaCl
H2SO4 KOH K2SO4
HCl Ca(OH)2 CaCl2
H2SO4 Mg(OH)2 MgSO4

24. C6.2 : Planning, Carrying out and controlling chemical
synthesis
1. Identify the stages in the chemical synthesis of an
inorganic compound.
• choosing the reaction or series of reactions
• risk assessment (chemical and procedural)
• working out the quantities of reactants to use
• carrying out the reaction in suitable apparatus in the right
conditions (such as temperature, concentration or the
presence of a catalyst)
• separating the product from the reaction mixture
• purifying the product
• measuring the yield and checking the purity of the product.

25. Understand the purpose of these techniques….
• Dissolving… forming solutions to allow easy mixing of
reactants
• Crystallisation… to purify a sample by the formation of pure
crystals from a cooled (often saturated) solution,
• Filtration… to separate solid impurities from a solution, or to
remove excess solid.
• Evaporation… to remove excess solvent from a solution
• Drying in an oven or dessicator… to remove water without
the risk of wasting yield.
• Titration… to find the concentration of an acid (or alkali)
using an alkali (or acid) of a known concentration AND an
indicator

26. Understand the importance of purifying chemicals and
checking their purity.
There are three main grades of chemicals :
1. Analytical – this is the most pure (and most expensive!)
If a product is to be used in foods/medicines then this
grade is needed – eg. Table salt.
2. Laboratory – this is the ‘medium grade’.
3. Technical – this is low grade purity – eg salt for gritting
roads.

27. Understand that a balanced equation for a chemical
reaction shows the relative numbers of atoms and
molecules of reactants and products.
Mg(s) + 2HCl(aq)  MgCl2(aq) +H2(g)
Reactants : 1 x Magnesium atom
2 x Hydrogen atoms
2 x Chlorine atoms
And, because the equation is balanced, the same
number of atoms are present for the products side!
The numbers in front of the formula tells you how
many molecules there are of it. So above, there are 2
molecules of HCl, and 1 molecule of everything else.

28. Understand that the relative atomic mass of an element
shows the mass of it’s atom relative to the mass of other
atoms.
Specifically, the RAM is compared to the mass of
Hydrogen.

29. Be able to use the periodic table to obtain the relative
atomic masses of elements.
Look at the periodic table in your planners.
The bottom number is the relative atomic mass.

30. Calculate the relative formula mass of a compound using
the formula and the relative atomic masses of the atoms it
contains.
Periodic table :
Ca = 40g C = 12g O = 16g
CaCO3 = 40+12+(3x16)
= 40+12+48
= 100g
What is the relative formula mass of calcium carbonate?
Formula of calcium carbonate = CaCO3

31. What is the relative formula mass of magnesium
chloride?
Formula of magnesium chloride = MgCl2
From the periodic table:
Mass of Mg = 24g Mass of Cl = 35.5g
MgCl2 = 24 + (2 x 35.5)
= 24 + 71
= 95g

33. 2Mg(s) + O2(g)  2MgO(s)
• 16g of oxygen (Relative formula mass = 32) is used
to make magnesium oxide (relative formula mass =
40).
How much magnesium oxide should we expect?
• 16/32 = 0.5
• Ratio is 1:2 for oxygen to magnesium oxide
• 2 X 0.5 X 40 = 40g yield of magnesium oxide
O
8
16 On periodic table

34. Mg(s) + 2HCl(aq)  MgCl2(aq) +H2(g)
• 2.4g of magnesium (Relative atomic mass = 24) is
used to make magnesium chloride (relative formula
mass = 95).
How much of this salt should we expect?
• 2.4/24 = 0.1
• Ratio is 1:1 for magnesium to magnesium chloride
• 0.1 X 1 X 95 = 9.5g yield of magnesium chloride

35. Calculate percentage yields given the actual and theoretical
yield.
actual mass of pure sample X 100
theoretical mass expected
Percentage
yield =
So if by experiment, 7.4g of magnesium chloride was
made, when theoretically 9.5g was expected; what is the
percentage yield?
% yield = 7.4
9.5
X 100 = 0.7789 x 100 = 77.8 % yield.

37. An acid-base titration is the determination of the
concentration of an acid or base by exactly
neutralizing the acid/base with an acid or base of
known concentration. This allows for quantitative
analysis of the concentration of an unknown acid or
soluble base. It makes use of the neutralisation
reaction that occurs between acids and bases and the
knowledge of how acids and bases will react if their
formulas are known.
Acid-Base titrations can also be used to find percent
purity of chemicals.
Titrations

40. • Open the tap to let the acid run
into the flask
• Stop the tap at the first sign of
a colour change
• Note the volume delivered
(this is approximate)
• Repeat, but add drop by drop
near the volume noted for
greater accuracy. Record
exact volume of acid needed
to get colour change for
neutral.
• Use the volumes of both
solutions and the
concentration of the acid to
find the concentration of the
alkali using a given formula
(This could be
a solid
dissolved in
water)
Describe how to carry out an acid alkali titration accurately.

41. Substitute results in a given formula to interpret titration
results quantitatively.
In a titration, 50cm3
of 2M sodium hydroxide was exactly
neutralised by 30cm3
of hydrochloric acid.
What is the concentration of hydrochloric acid?
Method
1. Write a balanced equation for the reaction.
sodium hydroxide + hydrochloric acid sodium chloride +
waterNaOH(aq)
HCl(aq) NaCl(aq) H2O(l)
2. Use the big numbers in front of the formulae ( if any) to
work out the proportion of NaOH to HCl.
In this case, it is 1:1 so 1 mole NaOH reacts with 1 mole HCl

42. 3. Find out how many moles of sodium hydroxide are
present.
(moles = [concentration (in M) x volume (in cm3
)] : 1000
The number of moles in 50cm3 of 2M sodium hydroxide
= (2x50) : 1000
= 0.1 moles of sodium hydroxide.
4. From part 1 and 2 we know that 30cm3 of HCl also
contains 0.1 moles.
So to find the concentration of acid you rearrange the
formula: concentration = (moles x 1000) : Volume
Conc = (0.1 x 1000) : 30
= 3.33 M

43. Understand why it is important to control the rate of a
chemical synthesis.
If it is too fast it could make it unsafe.
(eg could get too hot if exothermic; gas could be
produced to quickly and pressure build up)
If it is too slow, then product would be made too
slowly, and yield low, so profit too low. (economic
factors)

44. Explain the term ‘rate of chemical reaction’.
This is the speed at which the reaction takes place.
A reaction takes place when reactant molecules collide
with enough energy .

45. Describe ways for following the rate of a reaction.
1. By collecting a gas.
2. Weighing the reaction mixture.
3. Observing colour change or precipitate.

46. Interpret results from experiments that investigate rate
of reactions.
Time (seconds)
Mass
lost
(g)
The reaction
starts off quickly
It slows down as
it proceeds.
It eventually stops when one
of the reactant particles
has run out.

47. Rate graphs and reactant concentrations
Amountofproduct
Time
reactants
product
Reactant Concentration falls
Rate of Reaction falls
All product
All reactant
Mix of reactant
And product
Gradient of graph decreases

48. Rates and Graphs
• These show the increasing amount of product or
the decreasing amount of reactant.
Amountofproduct
Time
Amountofreactant
Time
Steep gradient
Fast reaction
Shallow gradient
Slow reaction
Steep gradient
Fast reaction
Shallow gradient
Slow reaction

51. Time
Mass
lost
Chips
Powder
Graph shows a
faster reaction
with powder.
Same final
volume of gas
made.
Increasing the temperature would have the same effect.

52. Recall that reaction rates vary with….
• particle size (surface area)
• concentration
• temperature.
Remember – to increase the rate of reaction, there
needs to be more successful collisions per second.

53. Surface area
• The reactions of solids can clearly only take place at the
surface of the solid.
• If we break a solid into smaller pieces we get more area and a
faster reaction.
Molecules collide with the
surface of the solid
Extra surface for molecules to
collide with.

54. • Reactions in solution involve dissolved particles that must
collide before reaction is possible.
• The more crowded (concentrated) the solution, the faster
the reaction because the frequency of successful collisions
increases.
Collisions infrequent Collisions frequent
Use simple collision theory to explain how rates of
reaction depend on the concentration of solutions of
soluble chemicals.

55. Understand that catalysts speed up a chemical reaction
while not being used up in the process.
Because they are not used up, they are recyclable.
For chemical reactions to occur:
• Existing bonds have to begin breaking so that new ones
can be formed.
• The molecules have to collide in such a way that the
reacting parts of the molecules are brought together.
Catalysts can help with either or both of these processes.