Stoichiometry Review Guide

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StoichiometryReview Guide
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What is stoichiometry?
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Multiple Choice

• In stoichiometry, chemists are mainly concerned
  with
• A. the types of bonds found in compounds.
• B. mass relationships in chemical reactions.
• C. energy changes occurring in chemical
  reactions.
• D. the speed with which chemical reactions
  occur.

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Name 2 ways we have used stoichiometry.
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What do the coefficients in a chemical equation
tell you?
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Multiple Choice

• Assume ideal stoichiometry in the reactionCH4
  2O2 ? CO2 2H2O
• If you know the mass of CH4, you can calculate
• A. only the mass of CO2 produced.
• B. only the mass of O2 reacting.
• C. only the mass of CO2 H2O produced.
• D. the mass of O2 reacting CO2 H2O produced.

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Which properties must be the same on both sides
of a chemical equation?
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Which properties dont have to be the same on
both sides of a chemical equation?
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2C2H6 7O2 ? 4H2O 6CO2Write 3 mole ratios
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2C2H6 7O2 ? 4H2O 6CO2For every ___ moles of
oxygen and ___ moles of ethane that react, ___
moles of carbon dioxide and ___ moles of water
are formed.
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Multiple Choice

• Which mole ratio for the equation 6Li N2 ?
  2Li3N is incorrect?
• A. C.
• B. D.

6 mol Li 2 mol N2
2 mol Li3N 6 mol Li
1 mol N2 6 mol Li
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2C2H6 7O2 ? 4H2O 6CO2Calculate in your head
how many moles of carbon dioxide are formed if
you begin with8 mols of ethane.
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What is a limiting reactant?
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Multiple Choice

• For the reaction below, how many moles of N2 are
  required to produce 18 mol NH3?
• N2 3H2 ? 2NH3
• A. 4.5 C. 18
• B. 9.0 D. 36

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What is an excess reactant?
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What is the Limiting Reactant? 2C2H6 7O2 ?
4H2O 6CO2 7.49 mol 24.6 mol
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Multiple Choice

• What mass of NaCl can be produced by the reaction
  of 0.75 mol Cl2?
• 2Na Cl2 ? 2NaCl
• A. 0.75 g C. 44 g
• B. 1.5 g D. 88 g

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Why is the LR not necessarily the reactant with
the least amount of moles?
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Multiple Choice

• What mass of CO2 can be produced from 25.0 g
  CaCO3 given the decomposition reaction
• CaCO3 ? CaO CO2
• A. 11.0 g C. 25.0 g
• B. 22.0 g D. 56.0 g

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How many moles of each product can be formed?
2C2H6 7O2 ? 4H2O 6CO27.49 mol
24.6 mol
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Multiple Choice

• If a chemical reaction involving substances A and
  B stops when B is completely used up, then B is
  referred to as the
• A. excess reactant.
• B. primary reactant.
• C. limiting reactant.
• D. primary product.

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How many grams of water can be formed? 2C2H6
7O2 ? 4H2O 6CO27.49 mol 24.6 mol
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Multiple Choice

• If a chemist calculates the maximum amount of
  product that could be obtained in a chemical
  reaction, he or she is calculating the
• A. percentage yield.
• B. mole ratio.
• C. theoretical yield.
• D. actual yield.

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How many moles excess reactant remain after the
reaction?2C2H6 7O2 ? 4H2O
6CO27.49 mol 24.6 mol
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Short Answer

• What data are necessary to calculate the
  percentage yield of a reaction?

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Extended Response

• A student makes a compound in the laboratory and
  reports an actual yield of 120. Is this result
  possible? Assuming that all masses were measured
  correctly, give an explanation.

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Extended Response

• Benzene, C6H6, and hydrogen bromide, HBr, as
  shown below. When 40.0 g of benzene are reacted
  with 95.0 g of bromine, 65.0 g of bromobenzene is
  produc with bromine, Br2, to produce
  bromobenzene, C6H5Br
• C6H6 Br2 ? C6H5Br HBr
• a. Which compound is the limiting reactant?
  b. What is the theoretical yield of
  bromobenzene? c. What is the reactant
  in excess, and how much remains after the
  reaction is completed? d. What is the
  percentage yield?