What are some specialproperties of solutions? Chemistry Unit 11
Main IdeasMixtures can be either heterogeneous orhomogeneousConcentration can be expressed in terms ofpercent or in terms of molesFactors such as temperature, pressure, andpolarity affect the formation of solutionsColligative properties depend on the numberof solute particles in a solution
ObjectivesCompare the properties of suspensions,colloids, and solutionsIdentify types of colloids and types ofsolutions.Describe the electrostatic forces incolloids
Types of MixturesHeterogeneous Mixtures are a combination of two or more pure substances in which each pure substance retains its individual properties. There are two main types of heterogeneous mixtures:
Types of Mixtures1. Suspensions – A suspension is a mixture containing particles that settle out if left undisturbed but, when stirred, the substance will flow like a liquid. • These substances are called thixotropic. These particles can be filtered out. Example : muddy water
Types of Solutions2. Colloids – A colloid is made of smaller sizes of suspension particles and these particles do not settle out. Particles cannot be filtered out. The most abundant substance in a mixture is the dispersion medium. Example: Milk • Colloids are categorized according to the phases of their particles.
ColloidsThe dispersed particles in a colloid areprevented from settling out because theyoften have polar or charged atomic groupson their surfaces. This results in theformation of electrostatic layers aroundthe particles.The layers electrostatically repel eachother when the dispersed particles collide,thus, the particles remain in the colloid.
ColloidsIf you interfere with the electrostaticlayering, colloid particles will settle outof the mixture. Heating also destroys acolloid because it gives collidingparticles enough kinetic energy toovercome the electrostatic forces andsettle out.
Brownian MotionBrownian motion is the jerky, randommovements of particles in a liquidcolloid, from the results of particlecollisions.
Tyndall EffectConcentrated colloids are often cloudy or opaque. Dilute colloids sometimes appear as clear as solutions. Dilute colloids appear to be homogeneous solutions because their dispersed particles are so small. The Tyndall effect is when dispersed colloid particles scatter light. Examples: sunlight through smoke filled air or fog
Homogeneous MixturesA homogeneous mixture is a solution of two or more substances that blend easily and constant composition throughout. There are different types of homogeneous solutions: A solution might exist as a gas, a liquid, or a solid, depending on the state of its solvent. Water is the most common liquid solvent. Examples: salt water and steel
Forming SolutionsSome combinations of substances readily form solutions, and others do not. A substance that dissolves in a solvent is said to be soluble in that solvent. Example: Sugar in water Two liquids that are soluble in each other are called miscible.
Forming SolutionsA substance that does not dissolve in a solvent issaid to be insoluble.Two liquids that cannot be mixed together butseparate shortly after are said to be immiscible
QuestionsMiscible substances are:A. two liquids that are not soluble in each otherB. solids that dissolve in liquidsC. solids that do not dissolve in liquidsD. two liquids that are soluble in each other
QuestionsThe jerky, random movement of particles in a liquid colloid is known as ____.A. Brownian motionB. Tyndall effectC. Charles’s LawD.kinetic energy
ObjectivesDescribe concentration using differentunitsDetermine the concentrations ofsolutionsCalculate the molarity of a solution.
Expressing ConcentrationConcentration can be expressed in terms of percent or in terms of moles. The concentration of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution.
Practice Problem #1In order to maintain a sodium chloride (NaCl) concentration similar to ocean water, an aquarium must contain 3.6g NaCl per 100g of water. What is the percent by mass of NaCl in the solution?Answer: 3.5%
MolarityMolarity is the number of moles of solutedissolved per liter of solution.Dilution equation: M1V1 = M2V2
Practice Problem #2A 100.5 ml intravenous (IV) solution contains 5.10 g of glucose (C6H12O6). What is the molarity of this solution?Ans: 0.282M
Practice Problem #3If you needed to make a 1.0 M solution of CaCl2, how many grams would you need to make 500 ml of it?5.5g
Practice Problem#4: DilutionWhat volume of 2.00 M calcium chloride stock solution would you use to make 0.50 L of 0.300 M calcium chloride solution?75 ml or .075L
MolalityMolality is the ratio of moles of solutedissolved in 1 kg of solvent.
Practice Problem #5In the lab, a student adds 4.5g of sodium chloride (NaCl) to 100.0g of water. Calculate the molality of the solution.0.77 mol/kg
Mole FractionMole fraction is the ratio of the numberof moles of solute in solution to thetotal number of moles of solute andsolvent. where XA and XB represent mole fractions of each substance
Practice Problem #6100 g of a hydrochloric acid solution contains 36 g of HCl and 64 g of H2O. What are the mole fractions of HCl and water?.22 HCl.78 H2O
QuestionWhich is NOT a quantitative measure of concentration?A. molarityB. molalityC. percent by massD.dilute
QuestionThe number of moles of solute divided by liters of solvution is called ____.A. molarityB. molalityC. percent by volumeD.percent by mass
Factors that Affect SolvationAgitation – shaken or stirred – agitationof the mixture allows for more contactbetween solute and solvent.Surface area – breaking the solute intosmall pieces helps solvation. A greatersurface area allows more collisions tooccur.
Factors that Affect SolvationTemperature – As temperatureincreases, the rate of solvation alsoincreases. Additionally, hotter solventsgenerally can dissolve more solidsolute.
SolubilitySolubility is the ability of a solvent to dissolve a solute. In an aqueous solution, a precipitate forms when a mixture produces an insoluble product.
Solubility Guidelines1. All common salts of the group 1 elements and ammonium ions are soluble.2. All common acetates and nitrates are soluble.3. All binary compounds of group 17 elements (other than F) with metals are soluble except hoes of silver, mercury (I), and lead.
Solubility Guidelines4. All sulfates are soluble except those of barium, strontium, lead, calcium, silver, and mercury (I).5. Except for those in Rule 1, carbonates, hydroxides, oxides, sulfides, and phosphates are insoluble.
Practice Problem #7Which of the following substances would be a precipitate in an aqueous solution? Why?a) NaClb) CaCO3c) Fe(NO3)d) KOH
SolubilityUnsaturated solutions – An unsaturated solution is one that contains less dissolved solute than the solvent can handle at a certain temperature and pressure. In other words, more solute can be dissolved in an unsaturated solution.
SolubilitySaturated solution – The maximum amount of solute has been dissolved in the solvent. The amount of crystallization is at equilibrium with the amount of solvation. In other words: The solution cannot dissolve anymore solute.
SolubiltyA supersaturated solution contains more dissolved solute than a saturated solution at the same temperature and are considered unstable. To make a supersaturated solution, a saturated solution is formed at a high temperature and then cooled slowly. The slow cooling allows the excess solute to remain dissolved in solution at the lower temperature.
Solubility of GasesGases, in general, are less soluble athigher temperatures than at lowertemperatures. At higher temperatures,the gases have a higher kinetic energythat allows them to escape from asolution.
Henry’s LawPressure affects the solubility of gaseous solutes in solutions. The solubility of a gas in any solvent increases as its external pressure increases. Carbonated beverages rely on the container to provide enough pressure to keep gas dissolved in the solution.
Henry’s LawHenry’s law states that at a giventemperature, the solubility (S) of a gasin a liquid is directly proportional to thepressure (P) of the gas. S1 S2 = P1 P2
Practice Problem #8If 0.85 g of a gas at 4.0 atm of pressure dissolves in 1.0 L of water at 25°C, how much will dissolve in 1.0 L of water at 1.0 atm of pressure and the same temperature?.21 g/ liter
QuestionFor a given amount, which type of solution contains the LEAST amount of solute?A. solvatedB. saturatedC. supersaturatedD.unsaturated
QuestionAt a given temperature, the solubility of a gas is directly proportional to what?A. volumeB. massC. molarityD.pressure
ObjectivesSolve solution stoichiometry problemsand solution limiting reactant problems.Determine excess concentration of ionsafter a reaction.
Solution StoichiometryStoichiometry applies to solutions too.The number of moles of a reactantand/or product can be found withconcentration using the concentrationequations.Most solution stoichiometry utilizes thenet ionic equation.
Solution StoichiometryConcentration of ions can be found in a solution by using the ratios in a compound. For example: 1.0 M CaCl2 has 1.0 mole of Calcium (Ca2+) in 1 liter of solution and 2.0 moles of chloride (Cl-)
Practice Problem #9What is the concentration of sodium ions in 1 liter of a 2.0 M solution of sodium sulfate?4.0 M
Practice Problem #10What mass of solid aluminum hydroxide can be produced when 50.0ml of 0.200 M Al(NO3)3 is added to 200.0 ml of 0.100 M KOH?
Practice Problem #11A 100.0 ml of 0.200 M aqueous potassiumhydroxide is mixed with 100.0 ml of 0.200 Maqueous magnesium nitrate. Write abalanced equation and net ionic equation.What mass of precipitate is produced andwhat is the concentration of each ionremaining in solution after the reaction iscomplete.
Practice Problem #12What mass of silver chloride can be preparedby the reaction of 100.0ml of 0.20 M silvernitrate with 100.0 ml of 0.15 M calciumchloride? Write the balanced equation andnet ionic equation. Calculate theconcentration of each ion remaining insolution after precipitation is complete.
Accumulating ContentHow does the net ionic change the waystoichiometry is calculated? What are thepros and cons?
Accumulating ContentHow does concentration affect solutions?
Accumulating ContentHow is solvation similar to ionic compounds?
Key ConceptsThe individual substances in aheterogeneous mixture remain distinct.Two types of heterogeneous mixtures aresuspensions and colloids.Brownian motion is the erratic movementof colloid particles.Colloids exhibit the Tyndall effect.
Key ConceptsA solution can exist as a gas, a liquid, or asolid, depending on the solvent.Solutes in a solution can be gases,liquids,or solids.Concentrations can be measuredqualitatively and quantitatively.
Key ConceptsMolarity is the number of moles of solutedissolved per liter of solution.Molality is the ratio of the number ofmoles of solute dissolved in 1 kg of solvent.
Key ConceptsThe number of moles of solute does notchange during a dilution. M1V1 = M2V2The process of solvation involves soluteparticles surrounded by solventparticles.
Key ConceptsSolutions can be unsaturated, saturated,or supersaturated.Henry’s law states that at a giventemperature, the solubility (S) of a gas ina liquid is directly proportional to thepressure (P) of the gas above the liquid.