Regents Review Stoichiometry Quiz

Empirical and Molecular Formulas

• The empirical formula for C6H12O6 is CH2O.
• If the empirical formula is CH2, the molecular formula could be C2H4, C3H6, C4H8, etc.

Molecular Mass and Formula Mass

• The formula H2O2 is an example of a molecular formula.
• The gram-formula mass of Ca3(PO4)2 is the sum of the atomic masses of calcium, phosphorus, and oxygen.
• The substance with the greatest molecular mass is the one with the largest sum of atomic masses of its constituent atoms.

Moles and Grams

• 0.250 mole of CuSO4·5H2O contains 1.25 moles of water.
• The total mass in grams of 0.75 mole of SO2 is calculated by multiplying the number of moles by the molar mass.
• The mass in grams of 1.00 mole of O2 gas is 32.0 g.

Atoms and Molecules

• The total number of atoms of oxygen in the formula Al(ClO3)3 is 13.
• The gram formula mass of Na2CO3·10H2O is the sum of the atomic masses of sodium, carbon, oxygen, and hydrogen.

Molecular Mass and Empirical Formula

• If the empirical formula is CH2O, the molecular mass could be 30, 60, 90, etc.
• A compound with an empirical formula of CH2 and a molecular mass of 56 has a molecular formula of C4H8.

Gas Density

• The density of a gas at STP is directly proportional to its molecular mass.
• The gas with the greatest density at STP is the one with the largest molecular mass.
• A sample of an unknown gas at STP with a density of 1.25 grams per liter has a gram molecular mass of 44.8 g.