Chemistry Year 1
SECTION
3
MOLE RATIOS, CHEMICAL
FORMULAE AND
CHEMICAL EQUATIONS
,SECTION3 MOLE RATIOS, CHEMICAL FORMULAE AND CHEMICAL EQUATIONS
PHYSICAL CHEMISTRY
Matter and its properties
INTRODUCTION
In this section, you will master essential skills, including IUPAC nomenclature
for inorganic compounds, writing compound formulas based on chemical laws,
and balancing equations. You will also engage in stoichiometric calculations to
deepen your understanding of chemical reactions.
At the end of this section, you should be able to:
• Use IUPAC nomenclature to name inorganic compounds, write the
formulae of compounds based on the laws of chemical combination and
write balanced chemical equations.
• Perform calculations involving stoichiometric relationship.
Key Ideas:
• Oxidation number is the charge of an ion in a compound.
• Empirical formula is the simplest ratio of atoms of each element in a
molecule.
• Molecular formula is the actual number of atoms of each element in a
molecule.
• Structural formula is a formula showing the arrangement of atoms in a
molecule.
• Prefix indicates the number of atoms of an element in a compound (e.g.,
mono-, di-, tri-, tetra).
• Suffix indicates the type of compound or ion (e.g., -ide, -ate, ite).
• Reactant is the substance present at the start of a chemical reaction,
which takes part in the reaction itself.
• Product is the substance formed as a result of a chemical reaction.
2
,SECTION3 MOLE RATIOS, CHEMICAL FORMULAE AND CHEMICAL EQUATIONS
• Stoichiometry is the relationship between reactants and products in a
chemical reaction.
• Coefficient is the number placed in front of a chemical formula in an
equation to balance the equation.
• Mole ratio is the ratio of the number of moles between two or more
substances.
• Yield refers to the amount (mass) of product obtained from a chemical
reaction.
• Actual yield is the amount of (mass) product obtained from a reaction in
practice.
• Theoretical yield: the maximum amount (mass) of product that could
be produced from a given amount of reactant, based on stoichiometric
calculations.
• Percent yield is the ratio of the actual yield to the theoretical yield,
expressed as a percentage.
• Limiting reagents are the reactants in a chemical reaction that are
consumed completely, and therefore limit the mass of the product formed.
• Excess reagents are the reactants that are left over when the reaction has
stopped.
NAMING INORGANIC COMPOUNDS USING
IUPAC NOMENCLATURE AND BALANCING THEIR
CHEMICAL EQUATIONS
The nomenclature of inorganic compounds is based on the oxidation number
system.
The oxidation number of an atom is the number of electrons gained or lost by an
atom when forming a compound.
Rules for Assigning Oxidation Number
1. The oxidation number of elements in their elemental state is zero.
2. The oxidation state of oxygen in most compounds is -2 except in peroxide
(-1) and superoxide (-½).
3
, SECTION3 MOLE RATIOS, CHEMICAL FORMULAE AND CHEMICAL EQUATIONS
3. The oxidation state of hydrogen is (+1). When it is bonded to a non-metal
and (-1) when bound to a metal.
4. The oxidation state of an ion is equal to the charge on the ion.
5. For a neutral molecule or polyatomic ion, the sum of the oxidation numbers
of all the atoms must be equal to the total charge on it.
Rules for Naming Binary Ionic Compounds
1. Name the cation (positive ion) first followed by the name of the anion
(negative ion).
2. The name of the cation is the name of the metal.
3. For metals with atomic numbers above 20, indicate the oxidation state in
Roman numerals and brackets.
4. The anions are named by replacing the suffix with ‘ide’
Example:
NaCl – Sodium chloride
FeCl3 – Iron (III) chloride
Rules for Naming Simple Acids
1. Use the prefix ‘hydro’, then the root name of the central atom.
2. Add the suffix ‘ic’ to the root name.
3. Add the word ‘acid’.
Example:
HCl – Hydrochloric acid
HI – Hydroiodic acid
Rules for Naming Oxoacids
1. Use the prefixes ‘oxo’, ‘dioxo’, ‘trioxo’ and ‘tetraoxo’ to indicate the number
of oxygen atoms present.
2. Add the root name of the central atom.
3. Add the suffix ‘ate’ followed by the oxidation state of the central atom in
Roman numerals and brackets.
4. Add the word ‘acid’.
4
SECTION
3
MOLE RATIOS, CHEMICAL
FORMULAE AND
CHEMICAL EQUATIONS
,SECTION3 MOLE RATIOS, CHEMICAL FORMULAE AND CHEMICAL EQUATIONS
PHYSICAL CHEMISTRY
Matter and its properties
INTRODUCTION
In this section, you will master essential skills, including IUPAC nomenclature
for inorganic compounds, writing compound formulas based on chemical laws,
and balancing equations. You will also engage in stoichiometric calculations to
deepen your understanding of chemical reactions.
At the end of this section, you should be able to:
• Use IUPAC nomenclature to name inorganic compounds, write the
formulae of compounds based on the laws of chemical combination and
write balanced chemical equations.
• Perform calculations involving stoichiometric relationship.
Key Ideas:
• Oxidation number is the charge of an ion in a compound.
• Empirical formula is the simplest ratio of atoms of each element in a
molecule.
• Molecular formula is the actual number of atoms of each element in a
molecule.
• Structural formula is a formula showing the arrangement of atoms in a
molecule.
• Prefix indicates the number of atoms of an element in a compound (e.g.,
mono-, di-, tri-, tetra).
• Suffix indicates the type of compound or ion (e.g., -ide, -ate, ite).
• Reactant is the substance present at the start of a chemical reaction,
which takes part in the reaction itself.
• Product is the substance formed as a result of a chemical reaction.
2
,SECTION3 MOLE RATIOS, CHEMICAL FORMULAE AND CHEMICAL EQUATIONS
• Stoichiometry is the relationship between reactants and products in a
chemical reaction.
• Coefficient is the number placed in front of a chemical formula in an
equation to balance the equation.
• Mole ratio is the ratio of the number of moles between two or more
substances.
• Yield refers to the amount (mass) of product obtained from a chemical
reaction.
• Actual yield is the amount of (mass) product obtained from a reaction in
practice.
• Theoretical yield: the maximum amount (mass) of product that could
be produced from a given amount of reactant, based on stoichiometric
calculations.
• Percent yield is the ratio of the actual yield to the theoretical yield,
expressed as a percentage.
• Limiting reagents are the reactants in a chemical reaction that are
consumed completely, and therefore limit the mass of the product formed.
• Excess reagents are the reactants that are left over when the reaction has
stopped.
NAMING INORGANIC COMPOUNDS USING
IUPAC NOMENCLATURE AND BALANCING THEIR
CHEMICAL EQUATIONS
The nomenclature of inorganic compounds is based on the oxidation number
system.
The oxidation number of an atom is the number of electrons gained or lost by an
atom when forming a compound.
Rules for Assigning Oxidation Number
1. The oxidation number of elements in their elemental state is zero.
2. The oxidation state of oxygen in most compounds is -2 except in peroxide
(-1) and superoxide (-½).
3
, SECTION3 MOLE RATIOS, CHEMICAL FORMULAE AND CHEMICAL EQUATIONS
3. The oxidation state of hydrogen is (+1). When it is bonded to a non-metal
and (-1) when bound to a metal.
4. The oxidation state of an ion is equal to the charge on the ion.
5. For a neutral molecule or polyatomic ion, the sum of the oxidation numbers
of all the atoms must be equal to the total charge on it.
Rules for Naming Binary Ionic Compounds
1. Name the cation (positive ion) first followed by the name of the anion
(negative ion).
2. The name of the cation is the name of the metal.
3. For metals with atomic numbers above 20, indicate the oxidation state in
Roman numerals and brackets.
4. The anions are named by replacing the suffix with ‘ide’
Example:
NaCl – Sodium chloride
FeCl3 – Iron (III) chloride
Rules for Naming Simple Acids
1. Use the prefix ‘hydro’, then the root name of the central atom.
2. Add the suffix ‘ic’ to the root name.
3. Add the word ‘acid’.
Example:
HCl – Hydrochloric acid
HI – Hydroiodic acid
Rules for Naming Oxoacids
1. Use the prefixes ‘oxo’, ‘dioxo’, ‘trioxo’ and ‘tetraoxo’ to indicate the number
of oxygen atoms present.
2. Add the root name of the central atom.
3. Add the suffix ‘ate’ followed by the oxidation state of the central atom in
Roman numerals and brackets.
4. Add the word ‘acid’.
4
