What is the osmolarity of the following solutions?
a. 0.35 M KBr
b. 0.15 M glucose + 0.05 M K₂SO₄

Verified step by step guidance

1. Step 1: Understand the concept of osmolarity. Osmolarity is a measure of the total number of solute particles in a solution. It is calculated by multiplying the molarity of each solute by the number of particles it dissociates into in solution, then summing up the contributions of all solutes.
2. Step 2: For part (a), determine the dissociation of KBr. Potassium bromide (KBr) is an ionic compound that dissociates completely in water into two ions: K⁺ and Br⁻. Therefore, the number of particles per formula unit is 2.
3. Step 3: Calculate the osmolarity for 0.35 M KBr. Multiply the molarity of KBr (0.35 M) by the number of particles it dissociates into (2). Use the formula: \( \text{Osmolarity} = \text{Molarity} \times \text{Number of particles} \).
4. Step 4: For part (b), analyze the dissociation of each solute. Glucose (C₆H₁₂O₆) is a molecular compound that does not dissociate in water, so it contributes 1 particle per formula unit. Potassium sulfate (K₂SO₄) is an ionic compound that dissociates into 3 ions: 2 K⁺ and 1 SO₄²⁻.
5. Step 5: Calculate the osmolarity for the mixture in part (b). For glucose, the contribution is \( 0.15 \times 1 \). For K₂SO₄, the contribution is \( 0.05 \times 3 \). Add these contributions together to find the total osmolarity: \( \text{Osmolarity} = (0.15 \times 1) + (0.05 \times 3) \).

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 accounts for all particles that contribute to the solution's osmotic pressure. For ionic compounds, osmolarity is calculated by considering the number of ions produced when the compound dissociates in solution.

Ionic Dissociation

Ionic dissociation refers to the process by which an ionic compound separates into its constituent ions when dissolved in a solvent, typically water. For example, potassium bromide (KBr) dissociates into K⁺ and Br⁻ ions. Understanding how many ions a compound produces upon dissociation is crucial for calculating its osmolarity.

Non-Electrolytes vs. Electrolytes

Non-electrolytes are substances that do not dissociate into ions in solution, such as glucose, while electrolytes do dissociate, like KBr and K₂SO₄. This distinction is important for osmolarity calculations, as non-electrolytes contribute only their molecular concentration, whereas electrolytes contribute based on the total number of ions formed from their dissociation.