10.3 Moles of Compounds

What is the mass of 8.35 moles of H₂SO₄

M. M. of H₂SO₄ = [(1.01 x 2)+32.1+(16 x 4)] = 98.12g/mol Mass = 8.35 moles x 98.12g/mol = 819.3 g H₂SO₄

How many moles are there in 229g of Mg(NO₃)₂?

M.M. of Mg(NO₃)₂ = [24.3+(14.01 x 2)+(16 x 6)] = 148.32g/mol Moles = 229g ÷ 148.32g/mol = 1.54 mols

Converting from Representative Particles to the Mass of a Compound. (2steps)

Mass of a compound = Representative Particles ÷ (6.02 x 10²³ R.P./mole) x Molar Mass of the Compound

Molar Mass of a Compound

Multiply each element's molar mass by the subscript of that element in the compound. Add these numbers together to find the molar mass of the compound.

(NH₄)₃PO₄

N = 14.01 x 3 = 42.03g/mol H = 1.01 x 4 x 3 = 12.12g/mol P = 30.97g/mol O = 16 x 4 = 64g/mol Molar Mass of (NH₄)₃PO₄ = 42.03 + 30.97 + 64 = 137 g/mol

Converting between Moles and Mass of a Compound

Mass of a compound = Moles x Molar Mass Moles of a Compound = Mass of the Compound ÷ Molar Mass

How many grams are in 4.83 x 10²⁵ atoms of MgO?

4.83 x 10²⁵ atoms MgO ÷ (6.02 x 10²³ R.P./mole) x 40.31g/mol = 3.234 x 10³ grams MgO

How many molecules are in 784 grams of CO₂?

784 grams ÷ 44 g/mol x 6.02 x 10²³ molecules/mole = 1.07 x 10²⁵ molecules CO₂

C₁₂H₂₂O₁₁

C = 12.01 x 12 = 144.12g/mol H = 1.01 x 22 = 22.22g/mol O = 16 x 11 = 176g/mol Molar Mass of C₁₂H₂₂O₁₁ = 144.12 + 22.22 + 176 = 342.34 g/mol

Converting from Mass to the Representative Particles of a Compound. (2steps)

Representative Particles = (Mass of the Compound ÷ Molar Mass) x 6.02 x 10²³ R.P./mole

Example: Ca₃(PO₄)₂

Ca = 40.078 g/mol x 3 = 120.23g/mol P = 30.97 x 1 x 2 = 61.94g/mol O = 16.00 x 4 x 2 = 128g/mol Molar Mass of Ca₃(PO₄)₂ = 120.23 + 61.94 + 128 = 310.17g/mol

Sr(NO₃)₂

Sr = 87.62g/mol N = 14.01 x 2 = 28.02 O = 16 x 3 x 2 = 96g/mol Molar Mass of Sr(NO₃)₂ = 87.62 + 28.02 + 96 = 211.64 g/mol

Find the Molar Mass (M.M.) of the following compounds:

Sr(NO₃)₂ (NH₄)₃PO₄ C₁₂H₂₂O₁₁