test 3: stoichiometry

solids to moles

mass (g) / molar mass (M)

liquids to moles

mass (g) = density (mL) x volume (g/mL)

gases to moles

pressure (atm) x volume (L) / gas constant (0.0821) x temperature (K)

aqueous to moles

concentration (M) x volume (L)

liters and milliliters

1 L = 1000 mL

moles to solids

moles (n) x molar mass (M)

moles to liquids

mass (g) = moles (n) x molar mass (M)

volume (mL) = mass (g) / density (g/mL)

steps to find percent composition

1) assume 1 mole of the compound

2) find the moles of each individual element

3) convert moles to grams

4) divide the individual masses of each element by the molar mass of the compound

5) convert decimals to percents by multiplying by 100

steps to finding the empirical formula

1) assume 100 grams of the compound

2) find the mass of each individual element in the compound

3) convert each element’s mass to moles

4) divide each mole value by the smallest mole value (mole ratio)

5) convert to whole numbers if needed

**6) determine the molecular formula of the compound

how to find the molecular formula

1) find the empirical formula mass (the mass of all the atoms in a compound’s whole number ratio)

2) divide the molar mass (given) by empirical formula mass (molar mass / efm)

3) multiply subscripts by the whole number

how to find the limiting reactant

moles of compound A = # atoms compound B / # atoms compound A

percent yield

actual (solve for this) yield / theoretical (given) yield x 100