Chapter 17: Problem 22
If a bottle of aspirin tablets has the aroma of vinegar, it is time to discard those tablets. Explain why, and include a chemical equation in the explanation.
Short Answer
Expert verified
A vinegar smell indicates aspirin hydrolysis, producing acetic acid.
Step by step solution
01
Understand the Problem
The aroma of vinegar in aspirin tablets indicates a chemical reaction has occurred. We need to understand what causes this change in smell.
02
Identify the Chemical Reaction
Aspirin (acetylsalicylic acid) can hydrolyze in the presence of moisture to form acetic acid and salicylic acid. The acetic acid is responsible for the vinegar smell.
03
Write the Chemical Equation
The chemical equation for the hydrolysis of aspirin is:\[ \text{C}_9\text{H}_8\text{O}_4 + \text{H}_2\text{O} \rightarrow \text{C}_7\text{H}_6\text{O}_3 + \text{C}_2\text{H}_4\text{O}_2 \]. Here, C₉H₈O₄ is aspirin, C₇H₆O₃ is salicylic acid, and C₂H₄O₂ is acetic acid (vinegar).
04
Explain the Significance
The presence of acetic acid indicates the aspirin has decomposed and thus may be less effective or safe to use. This is why the tablets should be discarded.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Hydrolysis Reaction
When aspirin is exposed to moisture, a chemical process called hydrolysis can occur. In this reaction, the aspirin molecules (known scientifically as acetylsalicylic acid) interact with water. As a result of this interaction, aspirin is broken down, leading to the formation of two new molecules: salicylic acid and acetic acid. The hydrolysis reaction can be expressed with the following chemical equation:\[ C_9H_8O_4 + H_2O \rightarrow C_7H_6O_3 + C_2H_4O_2 \]
- \(C_9H_8O_4\) is aspirin, the original substance.
- \(H_2O\) represents water, which facilitates the reaction.
- \(C_7H_6O_3\) is salicylic acid, one of the products formed.
- \(C_2H_4O_2\) is acetic acid, also known as vinegar.
Aspirin Stability
Aspirin's stability is a key factor in its effectiveness as a medication. This stability can be affected by environmental factors such as moisture and temperature. When aspirin tablets are stored improperly, they become susceptible to hydrolysis.
Over time, if aspirin is exposed to humid conditions or moisture, it breaks down as described in the hydrolysis reaction. This not only decreases the stability of the drug but also its potency and effectiveness.
To ensure aspirin remains stable and effective, it is vital to store it in a cool, dry place. Proper packaging generally helps protect aspirin from moisture, but additional care should be taken if there's a noticeable smell of vinegar.
Also, consider these points:
- High temperatures can accelerate hydrolysis even in sealed containers, leading to quicker degradation.
- Humidity can initiate the same process, degrading aspirin faster than expected.
Acetic Acid Formation
Acetic acid, also known as ethanoic acid, is responsible for the distinct vinegar smell. In the context of decomposing aspirin, acetic acid forms as a result of hydrolysis.As aspirin molecules break down, they release acetic acid. This is why old or improperly stored aspirin tablets often give off this characteristic smell. Acetic acid itself is a simple carboxylic acid (\(C_2H_4O_2\)) which is well known for giving vinegar its sour taste and smell.The presence of acetic acid in aspirin tablets indicates a decomposition process has occurred. This transformation signals that aspirin might have lost its intended medicinal properties and can potentially be less safe or ineffective for therapeutic use.Key points to remember:
- The aroma of acetic acid can serve as a natural indicator of aspirin degradation.
- Visible signs like packaging condensation can also point to hydrolysis occurring.
- Always ensure aspirin is stored appropriately to prevent acetic acid formation due to breakdown.