Lesson 7: 3.7 Solutions and Mixtures
Duration of Days: 1
Lesson Objective
Calculate the concentration of a solute in a solution or represent a mixture at the particulate level.
How do we quantitatively measure and express the concentration of a chemical solution?
How can particulate diagrams be used to represent the accurate ratio of solute particles to solvent particles?
Solute
Solvent
Molarity
Aliquot
Dilution
Homogeneous
Concentration
Learning Objective 3.7.A; Suggested Skill 5.B (Mathematical Routines).
Covers the math behind solutions. Students must master Molarity (M = moles of solute / Liters of solution) and understand how to calculate dilutions using M1V1 = M2V2. They must also map these calculations onto particulate models.
Support: Provide an algebraic "Molarity Triangle" visual to help students rearrange the equation easily to isolate moles, volume, or concentration.
Extension: Design a task where students must determine the final molarity of an individual ion (e.g., Cl^-) when two distinct salt solutions (like NaCl and CaCl2) are poured into the same beaker.
A student prepares a stock solution by dissolving 23.4g of pure sodium chloride (NaCl, molar mass = 58.44g/mol) into enough water to make 500.0mL of solution. The student then takes a 50.0mL aliquot of this stock solution and dilutes it with water to a final volume of 250.0 mL. Calculate the molarity of the final diluted solution.