Ch. 14 SOLUTIONS Ch. 14 SOLUTIONS GCC CHM 130

What is a solution? solution - A solute dissolved in a solvent –solute - chemical there’s less of –solvent - chemical there’s more of Water is the most common solvent.

Gas in Liquid Carbonated Soda Liquid in Liquid Vodka and tonic Solid in Liquid Salt Water Gas in Gas Air (N 2 + O 2 + trace gas) Solid in Solid Steel (Fe + C) Gas in Liquid Carbonated Soda Liquid in Liquid Vodka and tonic Solid in Liquid Salt Water Gas in Gas Air (N 2 + O 2 + trace gas) Solid in Solid Steel (Fe + C) Physical states of solute and solvent can be solid, liquid or gas Examples:

14.1 Gas solubility in liquids 1.Temperature: Solubility of a gas in a liquid ___________as T increases. Think about what happens if you open a can of soda that has been sitting outside for a few hours on a hot Summer day? decreases  T increases, gas molecules move faster, escape from surface easier.

2) Pressure: Solubility of a gas __________ as the pressure increases. increases Higher pressure keeps the liquid molecules from escaping into gas by pushing down on them. Another example – as divers descend in the ocean, the solubility of air in blood increases

Solid Solubility in liquids The solubility of a solid will _________ as the temperature increases. increase As T increases, molecules move faster and pull apart the ions in an ionic solid, so it dissolves faster as well. The solubility of a solid is not affected by pressure, unlike a gas.

14.2 Liquids in liquids “Like dissolves like” rule  Polar solutes dissolve in polar solvents  Nonpolar dissolves in nonpolar  Nonpolar and polar don’t mix  When two liquids mix we call them miscible, if they don’t mix they are immiscible

14.3 Solids in liquids “Like dissolves like” rule  Polar solutes dissolve in polar solvents  Nonpolar dissolves in nonpolar  Nonpolar and polar don’t mix  If a solid dissolves it is soluble, if not it is insoluble  Note - Solubility rules are for ionic solid solutes in water solvent!!! But not all solvents are water….

Will these solutes dissolve in these solvents? SolventSolute HCl Solute I 2 Solute PCl 3 Solute CH 4 NH 3 C 12 H 26 Br 2 Y YY Y Y Y No

Solutes  polar solventnonpolar solvent polar liquid nonpolar liquid polar solid nonpolar solid ionic solid miscible immiscible soluble insoluble Check Solubility Rules! Miscible, immiscible, soluble or insoluble

Which is soluble in oil? Which is miscible in oil? (Hint – is oil polar or nonpolar?) I 2 (s) KCl (s) P 4 (s) grease(s) HBr (l) CCl 4 (l) I 2, P 4, grease CCl 4 Nonpolar chemicals mix with oil – “like dissolves like” nonpolar ionic nonpolar nonpolar polar nonpolar

14.4 THE DISSOLVING PROCESS solvent molecules pull the solute molecules from each other if the solute- solvent attraction is greater than the solute-solute attraction

14.8 Concentration concentrated solution – lots of solute dilute solution – little solute If your drink is “strong,” it is concentrated. If your coffee is “weak,” it is dilute.

Concentration concentration.The amount of solute in solvent is the concentration. Units for concentration: - Mass Percent (%) - Molarity (M) concentration.The amount of solute in solvent is the concentration. Units for concentration: - Mass Percent (%) - Molarity (M)

14.8 Mass % = x 100 Ex: Calc. the mass % for 15.0 grams of potassium nitrate being dissolved in 135 grams of water. Mass % = (15.0g / g) x 100 = 10.0%

Ex: How many grams of water are needed to make a 5.00% saline solution with 10.0 grams of salt? 5.00 ( x) = 10.0 (100) 5.00 ( x) = x = 1000 / x = 200 X = 1.90x10 2 grams check: 5.00 = (10/200) (100) Yes First set up: 5.00% = (100)

14.9 Molarity MOLARITY (M) = moles per liter M = moles solute = mol liters of solution L MOLARITY (M) = moles per liter M = moles solute = mol liters of solution L

Ex: Calculate the molarity if 9.99 grams of potassium bromide is dissolved in 2.50 liters of water g KBr ( mol / g) = mol M = mol / 2.50 L = mol/L Do the questions in the online notes and worksheet !!!

Self Test Page 410 Try 1-4, 8-9, Answers in Appendix J