Mole to Mole

• Mass to Mass Problems involve one additional conversion
• Start from mass A convert to moles A then convert to Moles B to convert to Mass B
• EX. Lead IV Nitrate reacts with 5.0g of Potassium iodide. How many grams of Lead (IV) nitrate are required for a complete reaction?

Pb(NO3)4 + 4KI -> PbI4 + 4 KNO3

5.0g (mass A)   x   mol/166g (Mole A)  x 1/4 (Mole B)  x 455.2/mol (Mass B) = 3.4g

• How many grams of O2 are produced from the decomposition of 3.0g of Potassium Chlorate?

2 KClO3 -> 2 K + Cl2 + 3 O2

3.0g x mol/290.7g x 3/2 x 32/mol = 1.0g

• When Solid Zinc reacts with hydrochloric acid what mass of hydrogen gas is produced when 2.5g of Zinc react?

Zn + 2 HCl -> ZnCl2  + H2

2.5g x mol/65.4 x 1/1 x 2/mol = 0.076g of H2

• If 100g of Octane are burnt in a car engine what mass of oxygen is needed?

2 C8H18 + 25 O2 -> 16 CO2 + 18 H2O

100g x mol/114 x 25/1 x 32/mol = 352 g