Stoichiometry Study Guide KEY
Chemistry
RHS – Mr. Moss
1. Define the following:
a. Stoichiometry-the study of the quantitative relationships between the amounts of
reactants used and the products formed by a chemical reaction.
b. Mole –The SI unit used to measure the amount of a substance that contains 6.02 x
1023 atoms of that substance.
c. Mole Ratio-The ratio between any two substances in a balanced chemical
equation.
d. Molar Mass-The mass in grams of one mole of any substance.
2. What relationships can be determined from a balanced chemical equation? The
relationships between particles, moles, and mass for all reactants and products.
3. Explain why mole ratios are central to stoichiometric calculations. Mole ratios allow for
the conversion from moles of one substance in a balanced chemical equation to moles of
another substance in the same equation.
4. What is the first step in all stoichiometric calculation? (Be careful.) Write a balanced
chemical equation.
5. How is molar mass used in some stoichiometric calculations? Molar mass is a
conversion factor for converting moles of a given substance to mass or mass of a given
substance to moles.
6. Find the molar mass of the following:
a. H2SO4 (sulfuric acid) 98.09 g/mol
b. ZnO (zinc oxide) 81.39 g/mol
c. NH4NO3 (ammonium nitrate) 80.05 g/mol
7. List the mole ratios of the following balanced chemical equation.
a. 2Al + 3Br2  2AlBr3
;
;
(Each one of these can be
inverted to form another mole ratio. This would give a total of 6 ratios.)
8. The carbon dioxide exhaled by astronauts can be removed from a spacecraft by reacting it
with lithium hydroxide (LiOH). The reaction is as follows: CO2 +2LiOH  Li2CO3 +
H2O. An average person exhales about 20 moles of CO2 per day. How many moles of
LiOH would be required to maintain two astronauts in a spacecraft for three days? It
would require 40 mol LiOH per astronaut per day. For two astronauts, it would be 80
mol LiOH per day. For three days, you would need 240 mol LiOH.
9. The following reaction occurs in plants undergoing photosynthesis. 6CO2 + 6H2O 
C6H12O6 + 6O2. How many grams of glucose (C6H12O6) are produced when 24.0 moles
of carbon dioxide reacts in excess water? 721 grams of glucose.
10. The exothermic reaction between liquid hydrazine (N2H2) and liquid hydrogen peroxide
(H2O2) is used to fuel rockets. The products of this reaction are nitrogen gas and water.
a. Write the balanced chemical equation. N2H2 + H2O2  N2 + 2H2O
b. How many moles of nitrogen gas are produced when 300 grams of hydrazine
react with the liquid hydrogen peroxide? 10.0 mol N2
How many grams of sodium hydroxide (NaOH) are needed to completely react with 50.0 grams
of sulfuric acid (H2SO4) to form sodium sulfate (Na2SO4) and water? 2NaOH + H2SO4 
Na2SO4 + 2H2O ; 48.0 grams of NaOH are needed.