Problem 59 - Introductory Chemistry Atoms First

Question

A student runs a reaction to prepare \(40.0 \mathrm{~g}\) of aspirin and yet recovers only \(15.5 \mathrm{~g}\). What is the percent yield?

Step-by-Step Solution

Answer

The percent yield of the aspirin reaction is 38.75%, calculated using the formula Percent Yield = \(\frac{Actual Yield}{Theoretical Yield}\) × 100 with an actual yield of 15.5 g and a theoretical yield of 40.0 g.

Step 1: Identify the Actual and Theoretical Yields

In this problem, the actual yield of aspirin is given as 15.5 g, while the theoretical yield of aspirin is given as 40.0 g.

Step 2: Calculate the Percent Yield

Use the formula for calculating percent yield: Percent Yield = (Actual Yield / Theoretical Yield) × 100 Plug in the known values: Percent Yield = (15.5 g / 40.0 g) × 100

Step 3: Solve for Percent Yield

Divide the actual yield by the theoretical yield and multiply by 100: Percent Yield = (0.3875) × 100

Step 4: Report the Final Answer

Multiply the fraction by 100 to obtain the percent yield: Percent Yield = 38.75% The percent yield for this reaction is 38.75%.

Key Concepts

Actual Yield

The actual yield is a fundamental concept in chemistry. It refers to the amount of product that is actually produced in a chemical reaction. This value is often less than what is theoretically expected due to a range of factors such as side reactions, incomplete reactions, or losses during product recovery. In the context of aspirins production, the student managed to produce 15.5 grams of aspirin. This is the actual yield.

• Actual yield is measured experimentally.
• Different from theoretical yield, which is an ideal calculated value.
• Important for calculating the efficiency of a reaction through percent yield.

Understanding actual yield is crucial as it gives insight into the practical aspects of performing chemical reactions, highlighting any potential discrepancies between the ideal and real-world scenarios.

Theoretical Yield

Theoretical yield is a key estimate in chemistry representing the maximum amount of product that can be generated from a chemical reaction, assuming perfect conditions and complete conversion of reactants. Calculating this involves a stoichiometric analysis based on the balanced chemical equation of the reaction. In our instance of producing aspirin, the theoretical yield was determined to be 40.0 grams.

• Assumes 100% conversion of reactants to product.
• Calculated using the stoichiometry of the reaction.
• Provides a baseline for calculating percent yield.

It acts as a benchmark to help compare what was expected versus what was obtained in reality, aiding both in assessing reaction efficiency and optimizing experimental conditions.

Aspirin Synthesis

Aspirin, a common pharmaceutical, is synthesized through an esterification reaction involving salicylic acid and acetic anhydride. This reaction results in aspirin and acetic acid. The synthesis is a classic example in organic chemistry labs.

• Salicylic acid reacts with acetic anhydride.
• Catalyzed by an acid, usually sulfuric acid or phosphoric acid.
• Produces aspirin (acetylsalicylic acid) and acetic acid as a byproduct.

Understanding this reaction provides a practical insight into organic synthesis techniques and teaches important skills in conducting reactions, purifying products, and calculating yields.

Chemical Reaction Calculations

Chemical reaction calculations are essential for determining various aspects of reactions, including stoichiometry, yields, and efficiencies. These calculations begin with balancing the chemical equation, which ensures that mass and atoms are conserved.

• Stoichiometry is used to relate amounts of reactants to products.
• Calculations often include determining moles and mass of substances.
• Used to calculate theoretical and percent yields.

Understanding these calculations is vital for successfully predicting reaction outcomes, optimizing conditions, and scaling up processes from laboratory to industrial scales. They help bridge the gap between theoretical chemistry and practical applications in laboratory settings.