Stoichiometry is a very practical area of chemistry concerned with calculating amounts involved in reactions.  If you are a chemist performing an experiment in a lab, you need to know what amounts of your reactants to mix together and you need to be able to predict the amounts of the products that will be formed.  Stoichiometry is from the Greek for “measuring elements” and it allows us to calculate amounts of the reactants and products using our balanced chemical equation.

Here is a link to a short video explaining what stoichiometry is and how to set up basic problems:

http://www.kentchemistry.com/links/Math/reactionstoich.htm

Here is a link to another short video which will walk you step by step through a stoichiometry problem:

http://chemcollective.org/activities/tutorials/stoich/reaction_stoi

Try the following practice stoichiometry problems below then check your answers by clicking the link at the bottom of the page.  To print these practice problems as a worksheet click here:  Stoichiometry Calculations Practice Worksheet

Part One:  Mole to Mole Problems

1. How many moles of sodium will react with water to produce 4.0 mol of hydrogen in the following reaction?

2Na(s) + 2H₂O(l) –> 2NaOH(aq) + H₂(g)

2. How many moles of lithium chloride will be formed by the reaction of chlorine with 0.046 mol of lithium bromide in the following reaction?

2LiBr(aq) + Cl₂(g) –> 2LiCl(aq) + Br₂(l)

3. Aluminum will react with sulfuric acid in the following reaction.

2Al(s) + 3H₂SO₄(l) –> Al₂(SO₄)₃(aq) + 3H₂(g)

a.  How many moles of H₂SO₄ will react with 18 mol Al?

b.  How many moles of each product will be produced?

4. Propane burns in excess oxygen according to the following reaction.

C₃H₈ + 5O₂ –> 3CO₂ + 4H₂O

a.  How many moles each of CO₂ and H₂O are formed from 3.85 mol of propane?

b.  If 0.647 mol of oxygen is used in the burning of propane, how many moles each of CO₂ and H₂O are produced? How many moles of C₃H₈ are consumed?

Part Two:  Mole to mass problems

1. Phosphorus burns in air to produce a phosphorus oxide in the following reaction:

4P(s) + 5O₂(g) –> P₄O₁₀(s)

a.  What mass of phosphorus will be needed to produce 3.25 mol of P₄O₁₀?

b.  If 0.489 mol of phosphorus burns, what mass of oxygen is used? What mass of

P₄O₁₀ is produced?

2. Hydrogen peroxide breaks down, releasing oxygen, in the following reaction:

2H₂O₂(aq) –> 2H₂O(l) + O₂(g)

a.  What mass of oxygen is produced when 1.840 mol of H₂O₂ decomposes?

b.  What mass of water is produced when 5.0 mol O₂ is produced by this reaction?

Part Three:  Mass to Mole Problems

1. Sodium carbonate reacts with nitric acid according to the following equation.

Na₂CO₃(s) + 2HNO₃ –> 2NaNO₃ + CO₂ + H₂O

1. How many moles of Na₂CO₃ are required to produce 100.0 g of NaNO₃?
2. If 7.50 g of Na₂CO₃ reacts, how many moles of CO₂ are produced?

2. Hydrogen is generated by passing hot steam over iron, which oxidizes to form Fe₃O₄,in the following equation.

3Fe(s) + 4H₂O(g) –> 4H₂(g) + Fe₃O₄(s)  

a.  If 625 g of Fe₃O₄ is produced in the reaction, how many moles of hydrogen are produced at the same time?

b.  How many moles of iron would be needed to generate 27 g of hydrogen?

Part Four:  Mass to Mass Problems

1. Calculate the mass of silver bromide produced from 22.5 g of silver nitrate in the following reaction:

2AgNO₃(aq) + MgBr₂(aq) –> 2AgBr(s) + Mg(NO₃)₂(aq)

2. What mass of acetylene, C₂H₂, will be produced from the reaction of 90. g of calcium carbide, CaC₂, with water in the following reaction?

CaC₂(s) + 2H₂O(l) –> C₂H₂(g) + Ca(OH)₂(s)

3. Chlorine gas can be produced in the laboratory by adding concentrated hydrochloric acid to manganese(IV) oxide in the following reaction:

MnO₂(s) + 4HCl(aq) –> MnCl₂(aq) + 2H₂O

a.  Calculate the mass of MnO₂ needed to produce 25.0g of Cl₂

b.  What mass of MnCl₂ is produced when 0.091g of Cl₂ is generated?

  Click here to see the answers to the stoichiometry practice problems