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Mastering Mixtures: Types, Separation, and Concentration in Solutions

Discover the various mixtures like suspensions, solutions, and colloids, along with methods for separating mixtures. Learn about concentration, calculating molarity, dilution, solubility, and colligative properties in solutions.

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Mastering Mixtures: Types, Separation, and Concentration in Solutions

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  1. Concentrations & Solutions Unit 12

  2. Mixtures • Combination of 2 or more different substances • Heterogeneous mixtures – can see the parts (trail mix) • Homogeneous mixtures – mixture appears uniform (Kool-aid)

  3. Types of Mixtures 1. Suspensions 2. Solutions 3. Colloids

  4. Suspension • Heterogeneous mixture • Particles remain mixed with liquid when stirred but separate spontaneously over time • Example – flour & water

  5. Suspension Flour & water

  6. Solution • Homogeneous mixture with even distribution of particles • Can be gas (air) or solid (brass) • Most often liquid • Solutes dissolved in solvent • Aqueous solution – water is solvent

  7. Solution

  8. Colloid • Stable heterogeneous mixture • Appears homogeneous to naked eye b/c even distribution • BUT components visible under microscope • Does not settle when left to stand

  9. Colloid

  10. Separating Mixtures • Decanting – pour off liquid

  11. Separating Mixtures • Centrifuge – spin to separate by density

  12. Separating Mixtures • Filtration – liquid through filter

  13. Separating Mixtures • Evaporation – leaves behind solid

  14. Separating Mixtures • Chromatography - based on dissolving rates

  15. Separating Mixtures • Distillation – separate by boiling point

  16. Concentration • Ratio of solute to solvent • Consistent throughout solution • Calculating concentration • Parts per million (ppm) • Molality (m) • Molarity (M) g solute 1 000 000 g solvent moles solute kg solvent moles solute L solution

  17. Molarity (M) • M is read as “molar” or “moles per liter” • Any amount with the same molarity will have the same concentration or ratio of solutes to solvent • So 1 mL of 1 M HCl has the same concentration as 20 L of 1 M HCl

  18. Preparing a Solution • When preparing a solution, you must have the correct total volume • 1.00 mole solute + 1.00 L solvent DOES NOT equal 1.00 M solution! • Instead you need 1.00 L total solution • So dissolve solute in small amount of solvent and then add more solvent to get the correct total volume of solution

  19. Calculating Molarity 0.30 moles of KBr are dissolved in 0.40 L of solution. What is the molarity? M = 0.30 moles KBr = 0.40 L solution 0.75 M KBr

  20. Calculating Molarity • What is the molarity of a KCl solution that has a volume of 400.0 mL and contains 85.0 g of KCl? • Two problems • Grams • mL

  21. Molarity Calculations • How many grams of CaCl2 are needed to make 625 mL of a 2.0 M solution?

  22. Dilution • Adding solvent to solutions to decrease the concentration • Does not change the number of moles of the solute that are present • M1V1 = M2V2

  23. Practice • 2.0 L of a 0.88 M solution are diluted to 3.8 L. What is the new molarity?

  24. Practice • You have 150 mL of 6.0 M HCl. What volume of 1.3 M HCl can you make?

  25. Solubility • The ability of a solute to dissolve in a solvent • Measured in terms of the amount of a solute that will dissolve in a given amount of solvent

  26. Solubility – “Like dissolves like” • Polar substances tend to dissolve in other polar substances • Nonpolar substances tend to dissolve in other nonpolar substances • Degree of polarity also matters • Miscible – liquids that are completely soluble in each other

  27. Solubility – “Like dissolves like” • Polar + nonpolar doesn’t usually dissolve • Immiscible – 2 or more liquids that do not mix with each other

  28. How can we speed the dissolving process? • Shaking or stirring • Increases the surface area contact between the solute & solvent • Increasing the temperature • More energy available for dissolving

  29. Effects of temp on solubility • ID trends • Least soluble • Most soluble • Extrapolate data • 200 g at 50 oC • Precipitate formed from cooling

  30. Saturation • There is a maximum amount of solute that can be dissolved • Saturated solution • Less than that maximum amount • Unsaturated solution • More than that maximum amount • Supersaturated solution

  31. Colligative Properties • Any physical effect of the solute on the solvent • Not specific to the solute present but rather caused by the presence of a solute • Examples • Boiling point elevation • Freezing point depression

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