Compounds and Stoichiometry Flashcards
Compounds
pure substances made of two or more elements
Molecule
combination of two or more atoms (same or different) held together by covalent bonds
smallest unit of compounds
Ionic compounds do not form true molecules because…
of the way ions orient themselves in the solid state
Formula Weight (amu)
weight of a ionic compound as it has no molecules
sum of atomic weights of the constituent IONS in compound
Molecular Weight (amu)
sum of all atomic weights of the ATOMS in a molecule
Mole
quantity of substance (atoms) equal to the number of particles found in for example 12 grams of Carbon or 16 grams of oxygen
Avogadros Number
number of particles, 6.022*10^23
one mole of a compound has a mass in grams equal to the ______ of a compound in amu
molecular/formula weight
Molar Mass (g/mol)
mass of one mole of compound ; not same as molecular weight
g = n * MM
Mass = moles * Molar Mass
Equivalents Examples
HCL - 1 mole of H
H2SO4 - 2 moles of H
H3PO4 - 3 moles of H
Na - 1 mole of electrons
Mg - 2 moles of electrons
Gram Equivalent Weight
amount of a compound (in grams) that produces one equivalent of particle of interest
Gram Equivalent = Molar Mass of compound / moles of particle within ccompound
ex: GEW = 62/2 = 31g for H2CO3
Determining Number of Equivalents in a Compound
Equivalents = Mass of Compound/ Gram Equivalent Weight
Normality (N)
measure of concentration
N = equivalents / L
ex: 1 N solution of acid = 1 mole per liter of Hydrogen
Normality and Molarity Relationship
Molarity = Normality / number of particles produced/consumed by solute
Structural Formula
show bonds between constituent atoms of compound
all atoms present but not necessarily how they are oriented and the bonds present
Law of Constant Composition
any pure sample of given compound will contain same elements in an identical mass ratio
Empirical Formula
simplest, whole number ratio of elements in the compound
ex: CH for benzene
Molecular Formula
gives the exact number of atoms of each element in the compound and is a multiple of the empirical formula
ex: C6H6 for benzene
Ionic compounds only have Empirical/Molecular Formulas
Empirical as the total number of atoms cannot be determined
Percent composition
percent o a specific compound that is made up of a given element
% = (Mass of element in formula / molar mass of ocompound) * 100
Determining Empirical/Molecular Formulas from Percentages
1) Find molecular weight
moles C = (% in decimal)(MM of compound) / (MM of C)
moles of H = ….
2) round to nearest whole number to find mole ratio
3) find empirical b dividing by highest common divisor
ex: C6H9 -> C2H3