SolutionsSolutions

SolutionSolution – homogeneous mixture – homogeneous mixture in which solute & solvent in which solute & solvent particles are evenly distributed particles are evenly distributed in one anotherin one another

solventsolvent – the dissolving medium; – the dissolving medium; thing that does the dissolving thing that does the dissolving

solutesolute –the dissolved particles; –the dissolved particles; thing that is dissolvedthing that is dissolved

solutes and solvents can be solutes and solvents can be solids, liquids, or gasessolids, liquids, or gases

SolubilitySolubility – amount of solute – amount of solute that dissolves in a quantity of that dissolves in a quantity of solvent at certain temperature solvent at certain temperature and pressureand pressure

Solutions can be: Solutions can be: a) a) unsaturatedunsaturated – contains less solute – contains less solute

than solvent can possibly dissolvethan solvent can possibly dissolve

b) b) saturatedsaturated – contains as much – contains as much solute as can be dissolved by solute as can be dissolved by solventsolvent

c) c) supersaturatedsupersaturated – contains – contains more solute than can more solute than can normally be dissolved by normally be dissolved by solvent; not very stable – solvent; not very stable – slight disturbance to solution slight disturbance to solution will cause solute to will cause solute to precipitate or crystallizeprecipitate or crystallize

Terms related to solubilityTerms related to solubility solublesoluble – substance that will dissolve in – substance that will dissolve in

a solventa solvent insolubleinsoluble – – substance that will not substance that will not

dissolve in a solventdissolve in a solvent misciblemiscible – when 2 liquids will dissolve – when 2 liquids will dissolve

in each other in any proportion (ex: in each other in any proportion (ex: water and ethanol)water and ethanol)

immiscibleimmiscible – when 2 liquids are – when 2 liquids are insolubleinsoluble (ex: water and oil)(ex: water and oil)

ElectrolytesElectrolytes

excellent conductors in liquid state or excellent conductors in liquid state or dissolved in water (aqueous)dissolved in water (aqueous)

In order for a solution to carry an electrical In order for a solution to carry an electrical current, it must contain ions that are free current, it must contain ions that are free to move.to move.– Acids, bases and ionic compounds all ionize Acids, bases and ionic compounds all ionize

(break into ions) in water to form free ions.(break into ions) in water to form free ions.

http://www.schooltube.com/video/http://www.schooltube.com/video/36d820507a4c220061eb/The-Basics-on-36d820507a4c220061eb/The-Basics-on-Electrolytes Electrolytes

Factors Affecting SolubilityFactors Affecting Solubility agitation of the systemagitation of the system – increases – increases

collisions between solute and solvent collisions between solute and solvent particlesparticles

particle sizeparticle size – smaller dissolves faster – smaller dissolves faster because more surface areabecause more surface area

temperaturetemperature – solutes generally dissolve – solutes generally dissolve faster at higher temps.faster at higher temps.

– – higher kinetic energy at higher temps.higher kinetic energy at higher temps.

– – stronger and more frequent collisions stronger and more frequent collisions between solute and solvent particlesbetween solute and solvent particles

- Exception: solubility of gases - Exception: solubility of gases inversely inversely proportional to temperatureproportional to temperature

Concentration of SolutionsConcentration of Solutions

MolarityMolarity – M – mols of solute per L – M – mols of solute per L of solutionof solution

Example: 5 M – dissolve 5 mol of Example: 5 M – dissolve 5 mol of solute in enough solvent to make 1 L solute in enough solvent to make 1 L of solutionof solution

Calculating molarity (M)Calculating molarity (M)

1.1. convert mass of solute (g) to mol using convert mass of solute (g) to mol using molar mass molar mass

2.2. convert volume of solution to Lconvert volume of solution to L

3.3. use formula:use formula:

MM = =

mols mols solutesolute

litersliterssolutionsolution

Example 1Example 1– What is the molarity of 2.3 moles of What is the molarity of 2.3 moles of

sodium chloride in 0.45 liters of solution?sodium chloride in 0.45 liters of solution?

MM = = mols mols solutesolute

litersliterssolutionsolution

M = M = 2.3 mol2.3 mol = 5.1 M = 5.1 M 0.45 L0.45 L

Example 2Example 2What is molarity of a solution prepared by What is molarity of a solution prepared by

dissolving 37.94 g of KOH in Hdissolving 37.94 g of KOH in H22O, then O, then diluting the volume to 500 mL?diluting the volume to 500 mL?

mass = mass = 37.94 g KOH 1 mol KOH 37.94 g KOH 1 mol KOH = = 0.676mol0.676mol 56.11 g KOH 56.11 g KOH

molar mass molar mass KOHKOH

volume = volume = 500 mL 1 L500 mL 1 L = 0.500 L = 0.500 L 1000 mL1000 mL

molarity = molarity = 0.676 mol0.676 mol = 1.35 M = 1.35 M 0.500 L0.500 L

DilutionsDilutions

stock solutionstock solution – mixture w/ high – mixture w/ high concentration of solute; can be concentration of solute; can be diluted by adding additional solvent diluted by adding additional solvent to get molarity neededto get molarity needed

use this equation to solve for use this equation to solve for unknown:unknown:

MM11 ·· V V11 = M = M22 ·· V V22

Example Example What is the molarity of a solution that is What is the molarity of a solution that is

made by diluting 50.0 mL of 4.74 M made by diluting 50.0 mL of 4.74 M solution of HCl to 250.0 mL?solution of HCl to 250.0 mL?

MM11 = 4.74 M = 4.74 M

VV11 = 50.0 mL = 50.0 mL

MM22 = ? = ?

VV22 = 250.0 mL = 250.0 mL

MM11VV11 = M = M22VV22

MM22 = 0.948 M = 0.948 M

““Like dissolves likeLike dissolves like”” Rule RuleI.I. Polar solvents dissolve ionic and polar Polar solvents dissolve ionic and polar

solutessolutes I.I. partial positive & negative charges of polar partial positive & negative charges of polar

molecules are attractive to one anothermolecules are attractive to one anotherI.I. Due to an uneven sharing of electrons in a moleculeDue to an uneven sharing of electrons in a molecule

II.II. polar solvents with partial + and – charges are polar solvents with partial + and – charges are attracted to + and – ions in ionic compoundsattracted to + and – ions in ionic compounds

II.II. Nonpolar solvents dissolve nonpolar Nonpolar solvents dissolve nonpolar solutessolutes

http://www.mhhe.com/physsci/chemistry/http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swfessentialchemistry/flash/molvie1.swf

The Uniqueness of Water!The Uniqueness of Water!

Structure of HStructure of H22OO Lewis Dot StructureLewis Dot Structure

VSEPR ShapeVSEPR Shape

Electronegativity (H=2.1 and O=3.5)Electronegativity (H=2.1 and O=3.5)

Hydrogen bondingHydrogen bonding

Physical Properties of Water Physical Properties of Water – Density of IceDensity of Ice– Universal SolventUniversal Solvent– High melting and boiling pointsHigh melting and boiling points– Cohesion (surface tension)Cohesion (surface tension)– Adhesion (capillary action)Adhesion (capillary action)– High specific heat (ability to hold heat)High specific heat (ability to hold heat)

ALL OF THESE ARE DUE TO THE ALL OF THESE ARE DUE TO THE STUCTURE OF WATER (polar and STUCTURE OF WATER (polar and

hydrogen bonds)!!!hydrogen bonds)!!!