Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry Properties of Solutions

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 What is one of the most important Substances on earth???????????? Water!!!!!!!!!!!!!!!!!!!!! What is one of its most valuable properties? Its ability to dissolve many different substances!!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Solutions... the components of a mixture are uniformly intermingled (the mixture is homogeneous).

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Solutions can be Gases Ex. Air Solids Ex. Brass Liquids Ex. Carbonated water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Focus is the properties of liquid solutions, particularly those containing water.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Water, The Common Solvent Aqueous Solutions Water is the dissolving medium, or solvent.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Figure 4.1 The Water Molecule is · Polar ·Bent

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 Some Properties of Water 4 Water is bent or V-shaped. 4 The O-H bonds are covalent. 4 Water is a polar molecule. Electrons are not equally shared. Unequal charge distribution. OH δ - δ + 4 Hydration occurs when salts dissolve in water. Polarity gives water ability to dissolve cpds.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Polar Water Molecules Interact with the Positive and Negative Ions of a Salt

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 SOLUTION COMPOSITION SOLUTE - SUBSTANCE BEING DISSOLVED SOLVENT – DISSOLVING MEDIUM IF SOLID IN A LIQUID, THEN LIQUID IS SOLVENT IF LIQUID IN LIQUID, THE LIQUID OF LARGER AMOUNT IS SOLVENT.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 SOLUTION HOMOGENEOUS MIXTURE Solvent – Dissolving medium Solute – Substance dissolved

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 A Solute 4 dissolves in water (or other solvent) 4 changes phase (if different from the solvent) 4 is present in lesser amount (if the same phase as the solvent)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 A Solvent 4 retains its phase (if different from the solute) 4 is present in greater amount (if the same phase as the solute)

Solution -Solution - homogeneous mixture Solvent Solvent – dissolving medium Solute Solute - substance being dissolved

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Factors Affecting how quickly solutions are formed (Rate of solution formation) Stirring or agitation Particle size (grinding/crushing) Temperature

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Solubility The amt of a solute that dissolves in a given amt of solvent at a specified temperature.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Solubility Saturated solution-- Contains the max. amt of solute for a given amt of solvent at constant T & P (g solute/ 100 g solvent) Unsaturated solution-- Contains less than the max. amt of solute for a given amt of solvent at constant T & P

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Solubility Supersaturated solution --Contains less than the max. amt of solute for a given amt of solvent at constant T & P

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Factors Affecting Solubility STRUCTURE EFFECTS -- LIKE DISSOLVES LIKE -- SOLUBILITY IS FAVORED IF SOLUTE AND SOLVENT HAVE SIMILAR POLARITIES. -- POLARITY DETERMINED BY MOLECULAR STRUCTURE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Solubility LIKE DISSOLVES LIKE Polar substances dissolve polar substances Nonpolar substances dissolve nonpolar substances

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 PRESSURE EFFECTS PRESSURE HAS --- LITTLE EFFECT ON SOLUBILITY OF SOLIDS AND LIQUIDS --- SIGNIFICANTLY INCREASES SOLUBILITY OF A GAS

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 Figure 11.5 A Gaseous Solute

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Henrys Law P = kC P = partial pressure of gaseous solute above the solution C = concentration of dissolved gas k = a constant The amount of a gas dissolved in a solution is directly proportional to the pressure of the gas above the solution.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 TEMPERATURE EFFECTS SOLUBILITY OF MOST SOLIDS IN WATER INCREASES WITH TEMPERATURE. SOLUBILITY OF SOME SOLIDS IN WATER DECREASE WITH TEMPERATURE.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Figure 11.6 The Solubilities of Several Solids as a Function of Temperature

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 SOLUBILITY OF GASES IN WATER DECREASES WITH INCREASING TEMPERATURE.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 Figure 11.7 The Solubilities of Several Gases in Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 The Composition of Solutions Important to know the Amount of Chemicals present in a Solution.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Solution Composition 1.Molarity (M) = 2.Mass (weight) percent = 3.Mole fraction ( A ) = 4.Molality (m) =

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Molarity Molarity (M) = moles of solute per volume of solution in liters:

Molarity Concentration of a solution total combined volume substance being dissolved

C. Molarity 2M HCl What does this mean?

C. Molarity Calculations How many grams of NaCl are required to make 0.500L of 0.25M NaCl? L soln 0.25 mol NaCl 1 L soln = 7.3 g NaCl =.125 mol NaCl g NaCl 1 mol NaCl.125 mol NaCl

C. Molarity Calculations Find the molarity of a 250 mL solution containing 10.0 g of NaF g NaF 1 mol NaF g NaF.283 NaF.25 L soln = 0.95 M NaF =.283 mol NaF

Percent Composition by Mass Mass of Solute Mass of Solution x100

Percent by Mass How many moles of solute are contained in 343 grams of a 23% aqueous solution of MgCr 2 O 7 ? 343g of solution 23% 100% 1 mol g MgCr 2 O 7 =0.329 mol of MgCr 2 O 7

Percent Composition by Volume Volume of Solute Volume of Solution x100

B. Percent by Volume Determine the percent by volume of toluene (C 6 H 5 CH 3 ) in a solution made by mixing 40.0 mL of toluene with 75.0 mL of benzene (C 6 H 6 ) mL toluene mL benzene= 115 mL total solution (40.0 mL toluene / 115 mL solution) 100 = 34.8% toluene

Mole Fraction Moles A Total Moles = Mole Fraction, Χ

Molality mass of solvent only 1 kg water = 1 L water

D. Molality Find the molality of a solution containing 75 g of MgCl 2 in 250 mL of water. 75 g MgCl 2 1 mol MgCl g MgCl 2 = 3.2 m MgCl kg water

D. Molality How many grams of NaCl are reqd to make a 1.54m solution using kg of water? kg water1.54 mol NaCl 1 kg water = 45.0 g NaCl g NaCl 1 mol NaCl

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 43 Standard Solution Solution whose concentration is accurately known.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 44 Figure 4.10 Preparation of a Standard Solution

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 45 Dilution Solutions are often prepared by diluting more concentrated solutions.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 46 Common Terms of Solution Concentration Stock - routinely used solutions prepared in concentrated form. Concentrated - relatively large ratio of solute to solvent. (5.0 M NaCl) Dilute - relatively small ratio of solute to solvent. (0.01 M NaCl)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 47 Solutions by Dilution Moles of solute after dilution EQUALS Moles of solute before dilution M 2 x V 2 = M 1 x V 1

Dilution What volume of 15.8M HNO 3 is required to make 250 mL of a 6.0M solution? GIVEN: M 1 = 15.8M V 1 = ? M 2 = 6.0M V 2 = 250 mL WORK: M 1 V 1 = M 2 V 2 (15.8M) V 1 = (6.0M)(250mL) V 1 = 95 mL of 15.8M HNO 3

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 49 Figure 4.11 (a) A Measuring Pipet(b) A Volumetric (transfer) Pipet