THE LANAGUAGE OF CHEMISTRY
o The last significant figure of a measurement may not always be accurate.
o The number of significant figures is equal to the number known for certain, plus one that is
o The number of significant figures is the same regardless the units.
o How accurate a measure is refers to how close the value is to the correct value.
o How precise a measure is when a calculation is made by giving the same answer at different
o A Chemical formula describes the combination of any substance. It shows the relative
number of each type of atom in a substance. It contains elemental symbols to represent
atoms and subscripted numbers to show the number of atoms of each type.
o Molecular formula describes the types and numbers of atoms present in the molecule.
o Binary compounds are the compounds that only contain two elements.
o Subscripted numbers refers ONLY to the atom before it.
o The difference between covalent and ionic compounds is the type of bonding.
o Ionic compounds are made up of only ions which are held together by attractive forces
between ions of opposite charges.
o Covalent compounds are bonding that involves the sharing of electrons between
o Anhydrous is when the compounds contains no water molecules.
o Structural formulas tell us structural information as it shows how atoms in a molecule are
o Structural formulas do not show accurate geometry of a compound because it is hard to
accurately show the 3D molecules in 2D.
o Catenation is the linking of identical atoms to form massive molecules. This is due to the
covalent inorganic compounds which are small molecules that exist as rings and chains.
o Isomers are molecules that have the same chemical formula but different chemical
o The balls represent atoms.
o The sticks represent the bonds.
o The distorted sphere represents the volume occupied by its electrons.
o The spheres joins together to build a molecule. Nomenclature
o The system for naming compounds.
o A group of one or more atoms within a molecule that is bonded together in a particular way.
Aldehyde and Ketones
o Carbonyl Group (C=O)
o Aldehydes always have the carbon atom of the carbonyl group bonded to at least one H
atom, hence it must always be at the end of a carbon chain.
o Ketones is always bonded to two other C atoms, thus it must never be at the end of a carbon
o Carboxyl acid (-COOH)
o Always found at the end of a carbon chain.
The nomenclature of Alkanes
o Alkanes are molecules that contain carbon and hydrogen where carbon are joined by single
Constitutional isomerism in Alkanes
o Compounds with the same chemical formula but a different order of attachment of the
constitute atoms. Chemical Reactions and Stoichiometry
o A chemical reaction is when new substances are form when two or more chemical species
o Reactants are on the left of a chemical equation.
o Products are on the right of a chemical equation.
o Reversible reaction is when the reactions of both reverse and forward occur.
o Qualitative analysis is when we find out what substances are present in a sample without
measuring their amounts.
o Quantitative analysis is where we measure the amounts of various substances in a sample.
o Stoichiometry is the relative amounts of products and reactants in a chemical reaction.
o Stoichiometric coefficients are the numbers infront of the formulae which shows how many
molecules of each kind among reactants and products. They can also refer to atoms and
o Stoichiometric coefficients are used to ensure the equation acts according to the law of
conservation mass. Atoms can’t be destroyed or created in a chemical reaction, thus we
must keep the equal before and after a reaction.
o One mole is the amount of substance contains the same number as atoms in 12g of Carbon.
o Empirical formulae is the simplest whole number ratio of atoms within a compound.
o M = m/n
The determination of chemical formulae
o Describing the relative masses of the elements in a compound is a list of percentages by
mass called the compound’s percentage composition.
o % by mass of element = (mass of element present in a sample/mass of whole sample) x 100
Determination of empirical formulae
o Molecular formula is when a formula gives the composition of one molecule.
o It is rare to get the mass of every element in a compound by the use of just one weighed
sample so two or more analyses on different samples are needed.
o Three steps to determine empirical formulae:
1. 100g of compound individual mass % become actual masses of the elements in 100g of
2. Convert the ratio of elements by mass to a ratio by amount – divide the mass of each
element by molar mass.
3. Divide the resulting numbers by the smallest, which gives the smallest whole-number
ratios of each