Chapter 13. Solutions

What is a Solution?  Solution - A solute dissolved in a solvent. Chapter 13: Solutions  solute - chemical there’s less of  solvent - chemical there’s more of  Water is the most common solvent.  When you make Kool-Aid, what is the solute and what is the solvent? What is a Solution? Physical states of solute and solvent can be solid, liquid or gas. Examples: Gas in Liquid Carbonated Soda Liquid in Liquid Vodka and tonic Solid in Liquid Salt Water Gas in Gas Air (N2 + O2 + trace gas) Solid in Solid Steel (Fe + C) Gas Solubility in Liquids Pressure: Solubility of a gas __________ as the pressure increases. Another example – as divers descend in the ocean, the solubility of air in blood increases 13.1 Gas Solubility in Liquids Temperature: Solubility of a gas in a liquid ____________ as T increases. What happens if you open a can of soda that has been sitting outside for a few hours on a hot summer day? Solid Solubility in Liquids  The solubility of a solid will _________ as the temperature increases.  The solubility of a solid is not affected by pressure, unlike a gas. 1 13.2 Liquid Solubility in Liquids • • • • “Like dissolves like” Polar solutes dissolve in polar solvents Nonpolar dissolves in nonpolar Nonpolar and polar don’t mix 13.3 Solid Solubility in Liquids • “Like dissolves like” still applies • Polar solutes dissolve in polar solvents • Nonpolar dissolves in nonpolar • Nonpolar and polar don’t mix • Miscible: when two liquids mix (both liquids have the same polarity) – coke and rum • Immiscible: when two liquids don’t mix (one is polar, the other is nonpolar) – water and oil • Soluble: when a solid dissolves in a liquid (both have the same polarity) – CF2H2 and H2O • Insoluble: when a solid doesn’t dissolve in a liquid (one is polar, the other is nonpolar) – CH4 and H2O Note - Solubility rules are for ionic solid solutes in water solvent!!! But not all solvents are water…. Miscible, immiscible, soluble or insoluble? Solubility in Liquids Will these solutes dissolve in these solvents? Solvent Solute HCl Solute I2 Solute PCl3 Solute CH4 Solutes polar solvent nonpolar solvent polar liquid nonpolar liquid NH3 polar solid C12H26 nonpolar solid Br2 ionic solid Polar or Nonpolar? Is each substance below polar or nonpolar? I2(s) KCl (s) P4 (s) grease(s) HBr (l) CCl4 (l) 13.4 The Dissolving Process  Solvent molecules pull the solute molecules from each other if the solute-solvent attraction is greater than the solute-solute attraction Is oil polar or nonpolar? Which of these is/are soluble in oil? Which of these is/are miscible in oil? 2 13.8 Concentration  Concentrated solution – lots of solute  Dilute solution – little solute Concentration  The amount of solute in solvent is the concentration.  If your drink is “strong,” it is concentrated. If your coffee is “weak,” it is dilute.  Units for concentration:  Mass Percent (%) = (mass solute / mass solution) x 100  Molarity (M) = moles solute / volume solution (in L) 13.8 Mass/Mass % = x 100 Ex: Calc. the mass % for 15.0 grams of potassium nitrate being dissolved in 135 grams of water. 13.8 Mass/Mass % Example: How many grams of water are needed to make a 5.00% saline solution with 10.0 grams of salt? • First set up: 5.00% = 13.9 Molarity  MOLARITY (M) = moles of solute per liter of solution M = moles solute liters of solution (100) Molarity Example: Calculate the molarity of a solution made by dissolving 9.99 grams of potassium bromide in 2500. milliliters of water. = mol L  Do the questions in the online notes and worksheet !!! 3 Practice Calculations 1) Calculate molarity if 5.0 g sodium phosphate is dissolved in 255 mL of H2O. 2) What mass of sugar is needed to make 100.0 grams of Chapter 13 Self-Test, p. 401  Try 1-2, 8-9, 13, 15  Answers in Appendix J a 25.0 % solution? 4