Balanced chemical equations allow us to calculate the quantities of reactants and products in the equation. When you know the quantity of one substance, you can calculate the quantity of any other substance. (By quantity, we will generally mean grams or moles but it could also refer to molecules, litres, tonnes, etc) Calculations using balanced chemical equations are called stoichiometric calculations. Stoichiometry is the calculation of quantities in chemical equations.

Sample Problems: 2H 2 S (g) + 3O 2(g) 2SO 2(g) + 2H 2 O (g) Interpret this balanced chemical equation in the following 4 ways: a)number of representative particles b)number of moles c)masses of reactants and products d)volumes of gases at STP

Mole to Mole Calculations Recall: Balanced equation for the production of ammonia. N 2(g) + 3H 2(g) 2NH 3(g) The most important interpretation of this is as follows: 1 mole nitrogen gas + 3 moles hydrogen gas produces 2 moles of ammonia. If you know how many moles of one substance is present, you can use the mole ratios from the balanced chemical equation as a conversion factor to determine the number of moles of any other substance in the equation. Using the above chemical equation, how many moles of ammonia are produced when 0.60 moles of nitrogen reacts with hydrogen?

EX. 2 : Calculate the number of moles of each reactant to make 7.24 moles of ammonia.

What mass of nitrogen monoxide is formed when 5.00 mol of nitric acid reacts with copper ?

How many molecules of oxygen gas will be used when mol of butane (C 4 H 10 ) are burned?

If 1.25 x atoms of Fe are used up, how many moles of hydrogen gas will be produced?

What volume of ammonia would be produced (at STP) when 5.7 moles of hydrogen gas are consumed ?