Ch. 4: Compounds and Stoichiometry Flashcards
molecular weight
the sum of the atomic weights of all the atoms in a molecule in atomic mass units (amu)
formulate weight
the sum of the atomic weights of the constituent ions in an ionic compound in atomic mass units (amu)
mole
quantity of any substance equal to the number of particles equal to Avogadro’s Number (6.023 E 23 mol^-1)
like a dozen eggs
molar mass
the mass of one mole of a compound, expressed in g/mol
formula for determining the number of moles of a sample substance is…
Moles = mass of sample (g) / molar mass (g/mol)
one mole of any compound has a mass in grams equal to what
the molecular or formula weight in amu
concept of equivalents
How many moles of the thing we’re interested in will one mole of a given compound produce
= mass of compound (g)/gram equivalent weight(g)
gram equivalent weight definition
the mass of a compound that provides one mole of the compound of interest
gram equivalent weight formula
gram equivalent weight = Molar mass/n
where n is the number of particles of interest produced/consumed per molecule of the compound in the reaction
Normality (N)
a measure of concentration
equivalents/L
Molarity (M)
Normality/n
where n is the protons/electrons/ions produced/consumed by the solute
Empirical Formula
simplest whole-number ratio of the elements in the compound
Peroxide (H2O2) - HO
Water (H2O) - H2O
does not exist for ionic compounds
Molecular Formula
exact number of atoms of each element in the compound
ex: H2O, C6H12O6, H2O2
Percent Composition formula
mass of element in compound/molar mass of the compound x100%
combination reactions description
A + B –> C
decomposition reactions description
A –> B+C
combustion reactions description
oxidation of a fuel (usually hydrocarbon fuel being oxidized by O2 or similar)
CH4 + 2O2 –> CO2 + 2H2O
single-displacement reaction description
atom or ion in a compound replaced by atom/ion of another element
A + BC –> AB + C
double-displacement reactions
elements from two different compounds swap places to form two new compounds
also called metathesis reactions
AB + CD –> AD + BC
neutralization reactions
specific type of double-displacement reaction; acid reacts with a base to produce a salt (and usually water)
HCl + NaOH –> NaCl = H2O
limiting reagent
the reactant that will be used up or consumed first in a reaction
excess reagent
the reactant that will remain after all of the limiting reagent is used up
Two principles that govern determination of limiting reactant
- All comparisons must be done in moles
2. Must consider absolute mole quantity AND rate at which mole quantity is consumed
theoretical yield
maximum amount of product that can be generated as predicted from the balanced reaction
