General chemistryLesson 2 of 3 in the course Stoichiometry of Chemical Reactions

Limiting Reactants, Yield Calculations, and Atom Economy

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

A balanced chemical equation gives the stoichiometric proportions in which reactants combine. In real reactions, however, reactants may not be supplied in those exact proportions. This lesson explains how to identify the reactant that limits product formation and the reactant left over.

The coefficients in a balanced chemical equation specify the stoichiometric ratio of the substances. For hydrogen reacting with chlorine,

All flashcards

Limiting reactant
The reactant consumed first, which determines the maximum amount of product that can form.
Theoretical and actual yield
Theoretical yield is the stoichiometric maximum; actual yield is the amount obtained experimentally.
Percent yield
The ratio of actual yield to theoretical yield, multiplied by 100%: actual yieldtheoretical yield×100%\frac{\text{actual yield}}{\text{theoretical yield}} \times 100\%.
Atom economy
The percentage of reactant mass represented in the desired product, based on the reaction equation.
Green chemistry
The design of chemical products and processes to minimize hazardous substances and waste.

Quiz questions

  1. What does theoretical yield represent?Answer: The maximum product amount predicted by stoichiometry under specified conditions.
  2. A reaction has a theoretical yield of 0.5072 g and an actual yield of 0.392 g. What is its percent yield?Answer: 77.3%
  3. Which situation can make actual yield lower than theoretical yield?Answer: A side reaction consumes reactants to form other products.
  4. What does atom economy assess?Answer: How much reactant mass is represented in the desired product.
  5. When reactants are not supplied in stoichiometric amounts, what is used with the balanced equation to determine theoretical yield?Answer: The amount of the limiting reactant.

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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