Stoichiometry :  Sample Problems
1. A sample contains 27.1 g of calcium oxide.  How many moles of calcium oxide are in the sample?
NOTE: Use the Periodic Table to find the molecular mass (grams per mole)
2. How many atoms are in 0.652 mol of iron?
NOTE: A mole is by definition 6.0220 x 1023 particles which can generally be rounded to 6.02 x 1023.
3. How many liters does 3.8 moles of O2 occupy at STP (standard temperature and pressure)?
NOTE: At STP, 1 mole of any gas = 22.4L.  STP is 273K (0C) and 1 atm.
4. A solution of NaCl has a molarity of 0.549 M.  How many moles are in 350. mL of this solution?
NOTE: Molarity is MOLES per LITER.  The volume in milliliters must be converted to Liters.
5. How many grams of sodium hydroxide are needed to make 250. mL of a 0.200 M solution?

6. How many grams of carbon dioxide are there in a container with a volume of 4.50L at STP?

7. How many moles of nitrogen are there in a 7.45 mol sample of ammonium phosphate?

8.  If 120. g of propane, C3H8, is burned in excess oxygen, how many grams of water are formed?

9. 90.0 g of FeCl3 reacts with 52.0 g of H2S.  What is the limiting reactant?  What is the mass of HCl produced?  What mass of excess reactant remains after the reaction?
NOTE: The limiting reactant is the reactant that limits the amount of product that can be formed and is completely consumed during the reaction.  The excess reactant is the reactant that is left over once the reaction has stopped due to the limiting reactant.  See notes limiting reactant.