# 3.E: Stoichiometry

1. Glycerol ($$\ce{C3H8O3}$$) is sold in drug stores as glycerine and is commonly found in soaps and shampoos.
1. What is the molar mass of glycerol?
2. What is the mass in grams of 1.00 mole of glycerol?
3. How many molecules are in one mole of glycerol?
4. How many grams are in 0.217 moles of glycerol?

1. Ammonia ($$\ce{NH3}$$) is the active ingredient in many kitchen cleansers.  How many atoms are in
1. one molecule of ammonia?
2. one mole of ammonia?
3. 3.40 grams of ammonia?

1. Sodium nitrite is a controversial food preservative added to processed meat and thought to form cancer-causing compounds when heated.  What are the mass percentages of each element in sodium nitrite?

1. A compound consists of 40.7% $$\ce{C}$$, 5.1% $$\ce{H}$$, and 54.2% $$\ce{O}$$?
1. What is its empirical formula?
2. The molar mass of this compound is 118 grams/mole.  What is the molecular formula of this compound?

1. A 25.0 gram sample of a compound made up of magnesium, carbon and oxygen contains 7.20 grams magnesium and 3.55 grams carbon.
1. Find the empirical formula of this compound.
2. Find the mass percentage of each element in this compound.
3. What is the mass of magnesium in a 13.9 gram sample of this compound?
4. What is the mass of this compound that contains 0.290 moles of carbon?

1. A sample of zinc is heated in air to form zinc oxide.  Assuming all of the zinc is converted to the oxide, use the data table below to calculate the empirical formula of zinc oxide.

mass of crucible                                            =   32.00 g

mass of crucible + zinc (before heating)   =   33.64 g

mass of crucible + oxide (after heating)    =   34.04 g

1. Balance the following equations:
1. the combustion of the rocket fuel diborane,

$$\mathrm{B_2H_6(l) + O_2(g) \rightarrow B_2O_3(s) + H_2O(l)}$$

1. the combustion of the poisonous gas, $$\ce{PH3}$$,

$$\mathrm{PH_3(g)+O_2(g)\rightarrow H_2O(l)+P_4O_{10}(s)}$$

1. Write a balanced equation for each of the following reactions:
1. the reaction of solid lithium with nitrogen to form solid lithium nitride.
2. the reaction between aqueous solutions of cobalt(III) nitrate and sodium hydroxide to form aqueous sodium nitrate and solid cobalt(III) hydroxide.
3. the reaction between solid zinc and aqueous hydrochloric acid in a single replacement reaction.
4. classify the reactions in (a) and (b).

1. Hydrogen sulfide, given off by decaying organic matter, is converted to sulfur dioxide in the atmosphere by the reaction:

$$\mathrm{2H_2S(g)+3O_2(g)\rightarrow 2SO_2(g)+2H_2O(l)}$$

1. How many moles of $$\ce{H2S}$$ are required to form 8.20 moles of $$\ce{SO2}$$?
2. How many grams of $$\ce{O2}$$ are required to react with 1.00 mole of $$\ce{H2S}$$?
3. How many grams of water are produced from 6.82 g $$\ce{H2S}$$?
4. If 12.0 grams of $$\ce{SO2}$$ are formed from 7.98 g of $$\ce{H2S}$$, what is the percent yield?
5. How many grams of $$\ce{SO2}$$ are produced starting from 2.66 g $$\ce{H2S}$$ and 3.00 g $$\ce{O2}$$?
Which reactant is limiting?

1. A gaseous mixture containing 7.50 mol $$\ce{H2 (g)}$$ and 9.00 mol $$\ce{Cl2 (g)}$$ reacts to form hydrogen chloride ($$\ce{HCl}$$) gas.
1. Write a balanced equation for the reaction.
2. Which reactant is limiting?
3. If all the limiting reactant is consumed, how many moles of hydrogen chloride are formed?
4. How many moles of the excess reactant remain unreacted?

### Extra Questions

1.  Sodium sulfate has the formula Na2SO4.

1. What is the mass percentage of each element in sodium sulfate?
2. How many grams of this compound contain 2.00 grams sulfur?

2.  A sample of tin (Sn) is heated in air to form a tin oxide.  Assuming all of the tin is converted to the oxide, use the data table below to determine the empirical formula of the tin oxide formed.

 mass of crucible =  31.50 g mass of crucible + tin (before heating) =  33.40 g mass of crucible + tin (after heating) =  33.91 g

3.  A compound is made up of 30.4% N and 69.6% O.

1. Find the empirical formula of this compound.
2. The compound has a molar mass of 92.0 grams/mole.  What is the molecular formula of this compound?

4.  Octane undergoes complete combustion to form carbon dioxide and water.

1. Balance the following chemical equation for the combustion of octane:

C8H18(l)   +       O2(g)    →       CO2(g)   +       H2O(l)

1. How many moles of oxygen are required to burn 1.00 mole of octane?
2. How many grams of octane are needed to produce 6.63 moles of water?
3. How many moles of CO2 are produced from the combustion of 101 grams of octane?
4. What mass of CO2 is produced when 4.77 grams of oxygen gas are used up?
5. How many molecules of water are produced by the combustion of 2.1 grams of octane?
6. What mass of CO2 is produced starting from 5.00 g O2 and 1.62 g C8H18?
7. What is the percent yield if 3.70 g of CO2 are produced starting from 1.62 g C8H18?

5.  A compound is 45.0% lead (Pb) and 55.0% iodine (I) by mass.  What is the empirical formula of the compound?  What is the name of this compound?