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Lecture

CHEM120 Lecture Notes - Lithium Nitride, Potassium Carbonate, Magnesium Bromide


Department
Chemistry
Course Code
CHEM120
Professor
Carey Bissonnette

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Chemical Compounds
Types of Chemical Compounds and their Formulas:
Covalent bonds, which involve a sharing of electrons between atoms, give rise to molecular
compounds.
Ionic bonds, which involve a transfer of electrons from one atom to another, give rise to ionic
compounds.
An empirical formula is the simplest formula for a compound.
The subscripts in an empirical formula are reduced to their simplest whole-number ratio.
A molecular formula is based on an actual molecule of a compound.
A structural formula shows the order in which atoms are bonded together in a molecule and by
what types of bonds.
A condensed structural formula is written on a single line.
Organic compounds are made up principally of carbon and hydrogen, with oxygen and/or nitrogen
as important constituents in many of them. Each carbon atom forms four covalent bonds.
Chemical combination of a metal and a non-metal usually results in an ionic compound. An ionic
compound.
An ionic compound is made up of positive and negative ions joined together by electrostatic
forces of attraction.
The formula unit of an ionic compound is the smallest electrically neutral collection of ions.
The Mole Concept and Chemical Compounds:
Formula mass: is the mass of a formula unit, in atomic mass units.
Molecular mass: is the mass of a molecule in atomic mass units.
The molar mass is the mass of one mole of compound - one mole of molecules of a molecular compound
and one mole of formula units of an ionic compound.
Density converts from volume to mass
Molar mass converts from mass to moles
Avogadro constant converts from moles to elementary entities (atoms)
The existence of an element in more than one molecular form, a situation referred to as allotropy. Thus,
oxygen exists in two allotropic forms, the predominantly abundant diatomic oxygen, O2, and the much
less abundant allotrope ozone, O3.
Composition of Chemical Compounds:
The molecular formula C2HBrClF3 tells us that per mole of halothane there are two moles of C atoms,
one mole each of H, Br, and Cl atoms, and three moles of F atoms.
Percent Composition:
1. Determine the molar mass of the compound.
2. Determine the contribution of the given element to the molar mass.
3. Formulate the ratio of the mass of the given element to the mass of the compound as a whole.
4. Multiply this ratio by 100% to obtain the mass percent of the element.
Combustion Analysis:
After combustion, all the carbon atoms in the sample are found in the CO2. All the H atoms are in the
H2O.
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