Problem 19 - Chemistry: An Atoms-Focused Approach

Question

Calculate the number of moles of solute contained in the following volumes of aqueous solutions of four over-thecounter pharmaceuticals: a. \(0.250 \mathrm{~L}\) of \(0.076 \mathrm{M}\) acetaminophen (for pain relief) b. \(2.11 \mathrm{~L}\) of \(0.193 \mathrm{~m} M\) chromalyn sodium (for hay fever) c. \(0.0475 \mathrm{~L}\) of \(5.73 \mathrm{~m} M\) benzocaine (in cough syrup) d. \(14.6 \mathrm{~L}\) of \(27.4 \mathrm{~m} M\) Benadryl (antihistamine)

Step-by-Step Solution

Answer

Question: Calculate the number of moles of solute in each of the following pharmaceutical solutions: a. 0.250 L of 0.076 M Acetaminophen b. 2.11 L of 0.193 M Chromalyn Sodium c. 0.0475 L of 5.73 M Benzocaine d. 14.6 L of 27.4 M Benadryl Answer: a. Acetaminophen: 0.019 mol b. Chromalyn Sodium: 0.407 mol c. Benzocaine: 0.272 mol d. Benadryl: 400 mol

Step 1: a. Acetaminophen

First, let's calculate the number of moles of acetaminophen in \(0.250 \mathrm{~L}\) of \(0.076 \mathrm{~\cancel{m}} M\) solution: n = C * V n = \((0.076 \mathrm{~\cancel{m}} M)(0.250 \mathrm{~L})\) n = \(0.019 \mathrm{~mol}\) of acetaminophen

Step 2: b. Chromalyn Sodium

Now, let's calculate the number of moles of chromalyn sodium in \(2.11 \mathrm{~L}\) of \(0.193 \mathrm{~\cancel{m}} M\) solution: n = C * V n = \((0.193 \mathrm{~\cancel{m}} M)(2.11 \mathrm{~L})\) n = \(0.407 \mathrm{~mol}\) of chromalyn sodium

Step 3: c. Benzocaine

Let's calculate the number of moles of benzocaine in \(0.0475 \mathrm{~L}\) of \(5.73 \mathrm{~\cancel{m}} M\) solution: n = C * V n = \((5.73 \mathrm{~\cancel{m}} M)(0.0475 \mathrm{~L})\) n = \(0.272 \mathrm{~mol}\) of benzocaine

Step 4: d. Benadryl

Lastly, let's calculate the number of moles of Benadryl in \(14.6 \mathrm{~L}\) of \(27.4 \mathrm{~\cancel{m}} M\) solution: n = C * V n = \((27.4 \mathrm{~\cancel{m}} M)(14.6 \mathrm{~L})\) n = \(400 \mathrm{~mol}\) of Benadryl (rounded to a whole number) So, the number of moles for each pharmaceutical solution are: a. Acetaminophen: \(0.019 \mathrm{~mol}\) b. Chromalyn Sodium: \(0.407 \mathrm{~mol}\) c. Benzocaine: \(0.272 \mathrm{~mol}\) d. Benadryl: \(400 \mathrm{~mol}\)

Key Concepts

Solution Concentration

Solution concentration is a fundamental concept in chemistry. It's all about the amount of solute, which is the substance dissolved, in a given volume of solvent, usually a liquid such as water. When talking about pharmaceuticals, knowing the concentration of the solution is essential. It indicates how much of the active ingredient is present in the medication, which directly affects how it should be used. This is important because:

• It allows for precise dosing of medications, ensuring patient safety and effectiveness.
• It helps in determining the solubility of compounds in the solvent.
• It ensures consistency and quality in pharmaceutical production.

Concentration is often expressed in terms of molarity, which we'll explore further in another section.

Pharmaceutical Solutions

In the context of pharmaceuticals, solutions refer to liquid preparations where a drug is dissolved and distributed throughout a solvent. The key here is that the active ingredients must be completely dissolved. This ensures that each dose is consistent and predictable. Pharmaceutical solutions offer many benefits:

• They provide a rapid onset of action since the drug is already in liquid form, facilitating quicker absorption into the bloodstream.
• They are easy to swallow, making them particularly suitable for children or the elderly who may have difficulty with tablets or capsules.
• They allow for flexible dosing, where the dose can be easily tailored by adjusting the volume consumed.

However, the formulation of pharmaceutical solutions must be precise to ensure stability and efficacy over time.

Molarity

Molarity is a way to express solution concentration that states the number of moles of solute per liter of solution. It is a central concept in chemistry and particularly vital in the preparation and use of pharmaceutical solutions. Molarity is expressed as M, and you calculate it using the formula:\[ M = \frac{n}{V} \]where:

• \( n \) is the number of moles of solute, and
• \( V \) is the volume of solution in liters.

This measurement is crucial for creating solutions with accurate dosages of active ingredients. Accurate molarity ensures that the medication's effects are predictable and reliable, which is critical for patient safety and treatment efficacy.

Moles of Solute

The concept of "moles of solute" refers to the amount of a substance present in a solution, measured in moles. It's essential to understand this in the context of chemical reactions and solution preparation. The number of moles of a solute can be determined by the formula:\[ n = M \times V \]where:

• \( n \) is the number of moles of solute,
• \( M \) is the molarity of the solution, and
• \( V \) is the volume of the solution in liters.

The mole is a standard scientific unit for measuring large quantities of very small entities such as atoms, molecules, or other specified particles. Understanding how to calculate moles of solute helps in formulating pharmaceuticals accurately, ensuring each dose contains the correct amount of active ingredient.