Lowell High School Chemistry Stoichiometry Online Help   Stoichiometry Practice Problems:     Practice Problem #1: Oxygen gas can be produced by decomposing potassium chlorate using the reaction below. If 138.6 g of KClO3 is heated and decomposes completely, what mass of oxygen gas is produced?               KClO3 (s)  -->  KCl (s)  +  O2 (g)                  [unbalanced]       Practice Problem #2: Identify the limiting reagent for the given combination of reactants. Calculate how many grams of whatever substance will be in excess and how many grams of HF will be made.               F2 (g)  +  NH3 (g)  -->  N2F4 (g)  +  HF (g)               [unbalanced]         5.33 mol    2.22 mol       Practice Problem #3: How many grams of aluminum sulfate are produced if 23.33 g Al reacts with 74.44 g CuSO4?               Al (s)  +  CuSO4 (aq) -->  Al2(SO4)3 (aq)  +  Cu (s)  [unbalanced]       Practice Problem #4: Given the following reaction, answer Parts A and B.               NaClO3 (s) -->  NaCl (s) + O2 (g)                  [unbalanced]   Part A: 12.00 moles of NaClO3 will produce how many grams of O2? Part B: How many grams of NaCl are produced when 80.0 grams of O2 are produced?