Solutions are mixtures where one substance dissolves in another. Concentration tells us how much solute is in a solution. We'll learn about different ways to measure concentration, like molarity and molality, and how to calculate them.

Moles help us count particles in substances. We'll explore how to use moles in solutions, make stock solutions, and dilute them. These skills are crucial for working with solutions in chemistry and beyond.

Measuring Concentration

Understanding Concentration and Molarity

• Concentration measures the amount of solute dissolved in a given amount of solution
• Molarity (M) expresses concentration as moles of solute per liter of solution
• Calculate molarity using the formula $M = \frac{\text{moles of solute}}{\text{liters of solution}}$
• Molarity applies to solutions where volume changes with temperature
• Use molarity for reactions occurring at constant temperature

Exploring Molal Concentration and Parts per Million

• Molal concentration (m) represents moles of solute per kilogram of solvent
• Calculate molality using the formula $m = \frac{\text{moles of solute}}{\text{kilograms of solvent}}$
• Molality remains constant regardless of temperature changes
• Parts per million (ppm) expresses very dilute concentrations
• Calculate ppm using the formula $\text{ppm} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 10^6$
• Use ppm for trace amounts of substances (water contaminants)

Moles and Solutions

Understanding Moles and Stock Solutions

• Mole represents 6.022 × 10^23 particles of a substance (Avogadro's number)
• Use moles to relate the number of particles to the mass of a substance
• Calculate the number of moles using the formula $\text{number of moles} = \frac{\text{mass of substance}}{\text{molar mass}}$
• Stock solutions consist of concentrated solutions used to prepare more dilute solutions
• Prepare stock solutions by dissolving a known amount of solute in a specific volume of solvent
• Store stock solutions for future use in making working solutions

Dilution Techniques and Calculations

• Dilution involves adding solvent to a solution to decrease its concentration
• Use the dilution equation $M_1V_1 = M_2V_2$ to calculate concentrations after dilution
• M₁ and V₁ represent the initial concentration and volume
• M₂ and V₂ represent the final concentration and volume
• Perform serial dilutions to create a series of solutions with decreasing concentrations
• Calculate the dilution factor using the formula $\text{Dilution Factor} = \frac{\text{Final Volume}}{\text{Initial Volume}}$