Use the formula: moles = mass ÷ molar mass
Measure the mass of the substance in grams
Find the molar mass in g/mol from the periodic table or formula
Divide the mass by the molar mass
Use the formula: moles = number of particles ÷ Avogadro’s number
Avogadro’s number = 6.022 × 10^23 particles/mol
Use the formula: moles = volume ÷ molar volume for gases at STP
Molar volume at STP = 22.4 L/mol
Use the formula: moles = concentration × volume for solutions
Concentration must be in mol/L
Volume must be in liters
Use the formula: moles = PV ÷ RT for gases
P = pressure, V = volume, R = gas constant, T = temperature in Kelvin