Module 4. Quantitative Analysis of Chemical Reactions


Solid-fuel rockets are a central feature in the world’s space exploration programs, including the new Space Launch System being developed by the National Aeronautics and Space Administration (NASA) to replace the retired Space Shuttle fleet (Figure 1). The engines of these rockets rely on carefully prepared solid mixtures of chemicals combined in precisely measured amounts. Igniting the mixture initiates a vigorous chemical reaction that rapidly generates large amounts of gaseous products. These gases are ejected from the rocket engine through its nozzle, providing the thrust needed to propel heavy payloads into space. Both the nature of this chemical reaction and the relationships between the amounts of the substances being consumed and produced by the reaction are critically important considerations that determine the success of the technology.

This module will describe the quantitative relations between the amounts of substances involved in chemical reactions.  The mole is a unit of measure that allows us to quantify, or count, things on the submicroscopic level, such molecules, atoms, and ions. The term stoichiometry refers to the quantitative relationships between amounts of reactants and products in a chemical reaction. By putting stoichiometry to use, we can employ a powerful predictive and analytical method for understanding chemical reactions.


An image is shown of a rocket that appears to have just passed through a layer of clouds as it travels skyward. A bright white light is seen in the upper right corner of the image. To the lower left appears the layer of clouds and the bottom of the rocket with fire projecting from the fuel cones at its base.
Figure 1. Many modern rocket fuels are solid mixtures of substances combined in carefully measured amounts and ignited to yield a thrust-generating chemical reaction. (credit: modification of work by NASA)

Learning Objectives for Quantitative Analysis of Chemical Reactions

  1. Define the unit of the mole and illustrate its application as a tool to convert among macroscopic and submicroscopic quantities.
  2. Use balanced equations to calculate quantities of reactants and/or products from appropriate data.
  3. Identify limiting reagents; calculate theoretical and percent yields of products and quantities of excess reagents.
  4. Determine empirical and chemical formulas using composition by mass, combustion analysis data, and molar mass information.
  5. Recognize heat as an intrinsic component of chemical reactions.
  6. Calculate molarity of a solution and solve stoichiometry problems using solution molarities.

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