Stoichiometry

Stoichiometry Problems #1

Use the following equation to answer the questions below:

                        Mg₃N₂(s)  +  3 H₂O(l)   ®    3 MgO(s)  +  2 NH₃(g)

a)  How many moles of NH₃ are formed from 1.80 moles of H₂O?

b)  How many grams of Mg₃N₂ are needed to form 0.892 moles of NH₃?

c)  How many grams of H₂O are needed to form 3.40 grams of NH₃?

d)  How many molecules of NH₃are formed when 0.90 moles of H₂O are used up?

Answers to Stoichiometry Problems #1

a)  1.80 mol H2O  x  2 mol NH₃   =  1.20 mol NH₃

                                3 mol H₂O

b)  0.892 mol NH₃  x  1 mol Mg₃N₂  x  100.9 g Mg₃N₂  =  45.0 g Mg₃N₂

                                   2 mol NH₃           1 mole Mg₃N₂

c)  3.40 g NH₃  x  1 mole NH₃  x  3 mol H₂O  x  18.0 g H₂O  =  5.40 g H₂O

                            17.0 g NH₃      2 mol NH₃       1 mol H₂O

d)  0.90 mol H₂O  x  2 mol NH₃  x  6.02 x 10²³ molecules NH₃ 

                                 3 mol H₂O                  1 mol NH₃
                                                                                            =  3.6 x 10²³ molecules NH₃