Question

The active ingredient in Pepto-Bismol \(^{\text {m }}\) (an over-the-counter remedy for upset stomach) is bismuth subsalicylate, \(\mathrm{C}_{7} \mathrm{H}_{5} \mathrm{BiO}_{4}\). Analysis of a 1.500-g sample of Pepto-Bismol yields \(346 \mathrm{mg}\) of bismuth. What percent by mass is bismuth subsalicylate? (Assume that there is no other bismuthcontaining compound in Pepto-Bismol.)

Short answer

Answer: The percent by mass of bismuth subsalicylate in the Pepto-Bismol sample is approximately 23.07%.

Step-by-step solution

Convert milligrams to grams

We are given the mass of bismuth in the sample as \(346\) mg, which we need to convert to grams. Since \(1 \mathrm{g} = 1000 \mathrm{mg}\), the conversion is: \(346 \mathrm{mg} \times \frac{1 \mathrm{g}}{1000 \mathrm{mg}} = 0.346 \mathrm{g}\)

Calculate mass percent of bismuth subsalicylate

Now that we have the mass of bismuth in grams, let's find the mass percent of bismuth subsalicylate using the formula given above: \(\mathrm{Mass\,percent} =\frac{\mathrm{Mass\,of\,bismuth}}{\mathrm{Total\,mass\,of\,Pepto-Bismol}} \times100 \% = \frac{0.346 \mathrm{g}}{1.500 \mathrm{g}} \times 100 \%\) Calculating this gives: \(\mathrm{Mass\,percent} \approx 23.07 \%\) Therefore, the percent by mass of bismuth subsalicylate in the Pepto-Bismol sample is approximately \(23.07 \%\).

Key concepts

Understanding Bismuth Subsalicylate

Bismuth subsalicylate is an active compound found in many over-the-counter medications, such as Pepto-Bismol, which are used for treating upset stomach, heartburn, and nausea. Chemically, it is denoted as \( \mathrm{C}_{7} \mathrm{H}_{5} \mathrm{BiO}_{4} \), illustrating that each molecule contains carbon (C), hydrogen (H), bismuth (Bi), and oxygen (O) atoms.

Its medicinal properties stem from bismuth's ability to coat ulcers and sores in the stomach, creating a protective barrier against stomach acid. Furthermore, it possesses anti-inflammatory and mild antibiotic properties. The safety and efficacy of bismuth subsalicylate make it a staple in home medicine cabinets. However, for a chemical analysis, knowing the exact composition by mass of each element within a compound is crucial, especially for dosage and manufacturing purposes.

Exploring Stoichiometry

Stoichiometry is a division of chemistry focused on the quantitative relationships between the reactants and products in chemical reactions. It is based on the conservation of mass and the concept of the mole. Stoichiometry allows chemists to predict the amounts of substances consumed and produced in a given reaction.

Stoichiometric Calculations

For instance, when determining the percent composition of an element in a compound, stoichiometry becomes a necessary tool to relate the mass of an element to the total mass of the compound. In the example of bismuth subsalicylate, stoichiometry helps to identify what portion of the compound's total mass is due to bismuth. This understanding is central to the creation of balanced chemical equations, the prediction of product yields, and the calculation of reactant quantities for chemical synthesis.

The Role of Chemical Analysis

Chemical analysis is essential in identifying and quantifying the substances within a mixture or compound. It ranges from simple techniques, such as weighing on a balance, to more complex methods like spectroscopy or chromatography. These procedures can determine the composition, structure, and properties of chemical substances.

To conduct a chemical analysis, various steps are followed. The process starts with sample preparation, followed by an analytical technique suited for the substance in question, and finishes with result interpretation. In the context of Pepto-Bismol's analysis to find the mass percent of bismuth, initial weighing of the sample, careful conversion of measurements, and the use of stoichiometric formulas are all part of the chemical analysis.

Mass Percent Calculation

The mass percent calculation determines how much of a specific element or compound is present in a mixture, relative to the total mass. Mass percent is a critical value in the formulation of compounds in the pharmaceutical industry, ensuring that each dose of medication contains the appropriate amount of active ingredient. By understanding the breakdown of these ingredients, professionals can maintain consistent drug quality and efficacy.