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Chapter 6 - The Mole and Mole Calculations
n=N/NA
n = m/M
m/M = N/NA
n = moles (mol)
N = particles (atoms, molecules, formula units..) (particles/mol)
NA = avogadro's constant (6.02 x 10^23 particles/mol)
m = mass (g)
M = molar mass (mass of 1 mole of substance, found on periodic table) (g/mol)
Chapter 7 - % composition
% composition 2 methods:
law of definite proportions
mass of element / mass of compound x 100%
Molar Mass of element(s) / Molar Mass of compound x 100%
Empirical Formula (lowest ratio of elements)
mass --> moles
moles --> subscripts
subscripts --> divide by lowest
subscripts --> multiply if needed (to get whole #)
Molecular Formula (actual subscripts)
r = Molar mass of Molecular formula / Molar Mass of Empirical Formula
Molecular formula subscripts = r x Empirical Formula Subscripts
Hydrates
ionic compounds that crystallize with water in their structure
Mass % of water = (total mass of sample - mass of anhydrous) / total mass of sample x 100%
Molecular formula: find moles of anhydrous and moles of water, divide by lowest
C- H Analyzer
Find % comp of H in H2O (Molar mass H2 / Molar mass H2O)
Mass H = % comp H x Mass H2O
Repeat for C in CO2
If Oxygen present: mass of O = Initial mass of compound - mass of H - mass of O
Convert all mass to moles (n=m/M)
Put moles as subscripts, divide by lowest and multiply to get whole #
POEM - to help you remember
% to Mass
Mass to Mole
Divide by Smallest
Multiply until Whole
CHAPTER 8 - STOICHIOMETRY
Mole Ratios
Writing and balancing equations
Stoichiometry: convert to moles, use mole ratio, convert back to mass or particles
Limiting Reactant: find the reactant that produces the LEAST amount of product
% Yield = actual yield / theoretical yield x 100%