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Topic: Solutions

Topic: Solutions. Aim: What are colligative properties of solutions? Do Now: Calculate the % by mass of a solution containing 5 g solute in 100 g solvent (water). HW:. Colligative Properties. Properties that change when the concentration of a solution changes. Kool-Aid!.

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Topic: Solutions

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  1. Topic: Solutions Aim: What are colligative properties of solutions? Do Now: Calculate the % by mass of a solution containing 5 g solute in 100 g solvent (water). HW:

  2. Colligative Properties • Properties that change when the concentration of a solution changes

  3. Kool-Aid! • Solution A: 1g Kool Aid in 200mL sol’n • Solution B: 10g Kool Aid in 200mL sol’n • Compare the following: • Color • Taste • Texture • Density • Boiling point • Freezing point

  4. Boiling Point Elevation • Molarity increases, BP increases • Addition of solute lowers vapor pressure • Key: adding solute increases BP of solvent • What effect would the following solutes have on the boiling points of their respective solutions? (MgCl2, KCl, C6H12O6) • MgCl2 (for example) increases BP most, b/c MgCl2 ionizes into 3 particles, whereas KCl ionizes into only 2 particles, and glucose, being a covalent compound, does not ionize and only contributes 1 particle. • Don’t salt your pasta water before adding the pasta! The water will boil at a temperature higher than 100oC!

  5. Freezing Point Depression • Molarity increases, FP decreases • The solute prevents the solvent molecules from forming a solid lattice structure (necessary for solidification) • Why ocean water doesn’t freeze • Why we use road salt – the water will freeze at a temperature lower than 0oC • If you don’t have road salt, break out the Morton’s – it’ll have a similar effect!

  6. Electrolytes • Electrolyte – substance that dissolves in water to give a sol’n that conducts electric current • Soluble cpds are electrolytes (Table F) • Non-Electrolyte – substance that EITHER dissolves in water to give a sol’n that does NOT conduct a current OR it is insoluble • Insoluble cpds are non-electrolytes (Table F) • When a solid dissolves in water, entropy (disorder) increases b/c the ions separate

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