n isotonic solution must be approximately 0.30 osmol/L. How much KCl is needed to prepare 175 mL of an isotonic solution?

Verified step by step guidance

1. Understand that an isotonic solution has the same osmotic pressure as another solution, typically bodily fluids, and is approximately 0.30 osmol/L.
2. Recognize that KCl dissociates into K⁺ and Cl⁻ ions in solution, contributing to the osmolarity. Therefore, 1 mole of KCl results in 2 osmoles.
3. Calculate the total osmoles needed for 175 mL of solution using the formula: \( \text{osmoles} = \text{osmolarity} \times \text{volume in liters} \).
4. Convert the volume from milliliters to liters: \( 175 \text{ mL} = 0.175 \text{ L} \).
5. Use the relationship between moles and osmoles to find the moles of KCl needed: \( \text{moles of KCl} = \frac{\text{osmoles}}{2} \).

Key Concepts

Osmolarity

Osmolarity is a measure of the total concentration of solute particles in a solution. It is expressed in osmoles per liter (osmol/L) and is crucial for understanding how solutions affect cell behavior, particularly in biological contexts. An isotonic solution has the same osmolarity as body fluids, preventing net movement of water across cell membranes.

Dissociation of Ionic Compounds

Ionic compounds, such as potassium chloride (KCl), dissociate into their constituent ions when dissolved in water. For KCl, it separates into K⁺ and Cl⁻ ions, effectively doubling the number of particles in solution. This dissociation is important for calculating osmolarity, as each ion contributes to the total particle count.

Molarity and Volume Calculations

Molarity is defined as the number of moles of solute per liter of solution. To prepare a specific osmolarity, one must calculate the required moles of solute based on the desired volume of solution. In this case, knowing the volume (175 mL) and the target osmolarity (0.30 osmol/L) allows for the determination of the mass of KCl needed to achieve the isotonic condition.