The document provides an overview of key chemistry concepts related to formulae, equations, and amount of substance including: 1) Definitions of common chemistry terms like elements, compounds, atoms, molecules, and ions. 2) Explanations of relative atomic mass, relative molecular mass, molar mass, moles, and the Avogadro constant. 3) How to write and balance chemical equations, including state symbols, and derive ionic equations from full equations. 4) Calculations involving molar concentration, mass concentration, empirical and molecular formulae, reacting masses from equations. 5) Use of the ideal gas law, molar volume of gases, and calculations involving

1. Topic 1: Formulae, Equations and
Amount of Substance
THAHSEEN

2. 1.1 know the terms ‘atom', 'element', 'ion',
'molecule', 'compound', 'empirical formula'
and 'molecular formula’
Elements : Substances which cannot be split into
simpler substances. Elements are composed of atoms
of the same kind.
Compounds: Pure substances which can be split into
simpler substances. Compounds are formed by the
combination of two or more atoms chemically bonded.
Atom : Atom is the smallest, electrically neutral
particle of an element or compound
which cannot exist on its own & they do take part in
chemical reactions.
Molecule : A molecule is the smallest electrically
neutral particle of an element or compound which can
exist on its own, and is formed by the union of atoms
chemically bonded. Eg: H2, O2, Cl2
Ion : An ion is an atom or group of atoms, which
carries an electric charge.

3. 1.2 know that the mole (mol) is the unit for the amount of a substance and be able to
perform calculations using the Avogadro constant L (6.02 x 1023 mol-1)
1.4 understand the terms:‘relative atomic mass’ based on the 12C scale, relative molecular
mass’ and ‘relative formula mass’, including calculating these values from relative atomic
masses, molar mass’ as the mass per mole of a substance in g mol-1, parts per million
(ppm), including gases in the atmosphere

4. Relative atomic mass (Ar)- the weighted mean
(average) mass of an atom compared to 1/12 of the
mass of an atom of 12C.
Relative molecular mass (Mr)- The sum of the
relative atomic masses of a molecule is the relative
molecular mass.
Molar mass (M)- the mass per mole of a substance; it
has the symbol M and unit g/mol.
Mole- the amount of substance that contains the
same no of particles as the no of carbon atoms in
exactly 12g of 12C.
Avogadro constant- 6.02 x 1023 mol-1, the
number of particles in one mole of a substance.

5. Parts per million (ppm) the number of parts of one substance in
one million parts of another substance; a measure used to
describe chemical concentration; usually, ‘parts’ refers to masses
of both substances, or to volumes of both substance.
1 ppm means 1 g in 1 000 000 g or 1 mg in 1 000 000 mg.
1 ppmv means 1 cm3 in 1 000 000 cm3/ 1 000 dm3
Concentration of solutions can be compared using parts per million or ppm

6. 1.3 write balanced full and ionic equations, including state symbols, for chemical reactions
unbalanced: Na + Cl2 --> NaCl
balanced: 2Na + Cl2 --> 2NaCl
STATE SYMBOL:
● (s) = solid
● (l) = liquid
● (g) = gas
● (aq) = aqueous (dissolved in water)
2AgNO3(aq)+CaCl2(aq) = 2AgCl(s)+Ca(NO3)2(aq)
Ionic equations show any atoms and molecules
involved and not the spectator ions.
● write the word equation out as a symbol
equation
● separate the ions
● remove spectator ions
● rewrite and "tidy up" the equation
Ionic half equation:
2H+(aq) + 2e- >> H2 (g)

7. 1.5 calculate the concentration of a solution in mol dm−3 and g
dm−3
Mass concentration (of a solution) the mass (in g)
of the solute divided by the volume of the solution
Molar concentration (of a solution) the amount (in
mol) of the solute divided by the volume of the
solution.

8. 1.6 be able to use experimental data to calculate empirical and molecular formulae
Empirical formula- the smallest whole-number ratio of atoms
of each element in a compound
Calculating empirical formulae
● Divide the mass, or percentage by mass, of each
element by its relative atomic mass
● Divide the answer by the smallest of the numbers.
● This gives whole number ratio

9. Molecular formula- the actual number of atoms of each element in a molecule

10. 1.7 be able to use chemical equations to calculate
reacting masses and vice versa, using the concepts of
amount of substance and molar mass

11. 1.8 be able to use chemical equations to calculate volumes of gases and vice versa, using:
i the concepts of amount of substance
ii the molar volume of gases
iii the expression pV = nRT for gases and volatile liquids

12. MOLAR VOLUME
The volume occupied by 1 mol of any gas; this is normally 24 dm3 or 24
000 cm3 at r.t.p.

13. IDEAL GAS: pV = nRT
p= pressure in pascals (Pa)
V= vol in cubic metre (m3)
T= temp in kelvin (K)
n= amt of substance in moles (mol)
R= gas constant (8.31 J/mol/K)

14. 1.9 be able to calculate percentage yields and percentage atom
economies (by mass) in laboratory and industrial processes,
using chemical equations and experimental results
Atom economy = molar mass of the desired product × 100%
sum of the molar masses of all products

15. THEORETICAL YIELD
ACTUAL YIELDThe actual mass obtained in a reaction.
The maximum possible mass of a product in a reaction, assuming
complete reaction and no losses.
PERCENTAGE YIELD The actual yield divided by the theoretical yield, expressed as
percentage.
Why the mass of reaction product
may be less than the maximum
possible?
● The reaction is reversible and so
may not be complete
● There are side-reactions that lead to
other products that are not wanted.
● The product may need to be
purified, which may result in loss of
product.

17. ATOM ECONOMY
● Addition reactions have 100% atom economy.
● Elimination and substitution reactions have lower atom
economies.
● Multistep reactions may have even lower atom economies.
the molar mass of the desired product divided by the sum of the molar masses
of all the products, expressed as a percentage.

18. 1.10 be able to determine a formula or confirm an
equation by experiment, including evaluation of the data

19. There can also be more than one
reaction for the same reactants.
Reacting masses can be used to
identify the correct formula, or
which of the reactions is occuring.

20. 1.12 be able to relate ionic and full equations, with state symbols, to
observations from simple test-tube experiments, to include:
I. displacement reactions
II. typical reactions of acids
III. precipitation reactions

21. Displacement reactions
METAL DISPLACEMENT IN AQUEOUS SOLUTION
Mg (s) + CuSO4 (aq) → Cu (s) + MgSO4 (aq)
Cu2+(aq) + SO42-(aq) + Mg(s) → Mg2+(aq) + SO42-(aq) + Cu(s)
Mg is added to CuSO4 blue solution becomes paler/colorless. Mg
appearance from silvery to brown. Redox reaction. More reactive
metal displaces less reactive.
METAL DISPLACEMENT IN SOLID STATE
2Al (s) + Fe2O3 (s) → Al2O3 (s) + 2Fe (s)
2Al (l) + 2Fe3+ (l) + 3O2- (l) → 2Fe (l) + 2Al3+ (l) + 3O2- (l)
It is a exothermic and redox reaction. It require high
temperature.
DISPLACEMENT REACTIONS W/
HALOGENS
Chlorine will displace bromine- metal
displacement is redox reaction.
2KBr (aq) + Cl2 (aq) → 2KCl (aq) + Br2 (aq)
Cl2(aq)+ 2K+(aq)+ 2Br-(aq) → 2K- + 2Br- +2Cl-
A reaction in which one element replaces another, less reactive,
element in a compound.

22. Typical reaction of acids
ACID WITH METALS
Metal + acid → salt + hydrogen
Bubbles of hydrogen gas form. H+ ions gain
electrons converted to H2(g), reduced.
ACID WITH METAL OXIDES AND INSOLUBLE
METAL HYDROXIDES
Metal oxide + acid → salt + water
Metal hydroxide + acid → salt + water
Neutralisation reaction: H+ with O2- or OH-
ACIDS WITH ALKALIS
Alkali + acid → salt + water
Temp rise is noticed. Neutralisation reaction: H+
react with OH-.
ACID WITH CARBONATES
Metal carbonate + acid → salt + water + carbon dioxide
Bubbles of CO2 gas form. Neutralisation reaction:
H+ react with CO32-.
ACIDS WITH HYDROGENCARBONATES
Sodium hydrogencarbonate (baking soda) + citric acid →
sodium citrate + water + carbon dioxide

23. Precipitation reactions Reaction in which an insoluble solid is formed when two solutions
are mixed.
Carbon dioxide Calcium hydroxide (limewater) White ppt/ cloudy Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
Sulfates Barium chloride/barium nitrate White ppt (BaSO4) Na2SO4 (aq) + BaCl2 (aq) → BaSO4 (s) + 2NaCl (aq)
Halides Silver ions/silver nitrate Cl (white) Br (cream)
I (yellow)
NaCl + AgNO3 → AgCl + NaNO3

24. Questions

44. Question
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