Unit 13: Solutions Unit 13: Solutions

Solution - Solution - homogeneous mixturehomogeneous mixture

Solvent Solvent – substance that – substance that dissolves the solutedissolves the solute

Solute Solute - substance - substance being dissolvedbeing dissolved

Solute Solute - KMnO- KMnO4 4 KMnOKMnO44 Solution SolutionSolvent Solvent - H- H22OO

SolvationSolvation Solvation – Solvation – the process of dissolvingthe process of dissolving

solute particles are separated and solute particles are separated and pulled into solutionpulled into solution

solute particles are surrounded by solute particles are surrounded by solvent particlessolvent particles

SolvationSolvation

StrongElectrolyte

Non-Electrolyte

solute exists asions only

- +

salt

- +

sugar

solute exists asmolecules

only

- +

acetic acid

WeakElectrolyte

solute exists asions and

moleculesView animation online.

SolvationSolvation

NONPOLAR

NONPOLAR

POLAR

POLAR

““Like Dissolves Like”Like Dissolves Like”

SolubilitySolubility UnsaturatedUnsaturated

When the solvent When the solvent holds holds lessless solute solute than it than it normally can at a given temperature.normally can at a given temperature.

SolubilitySolubility SaturatedSaturated

When the solvent holds When the solvent holds as muchas much of a of a solutesolute as it normally can at a given as it normally can at a given temperature.temperature.

SolubilitySolubility SupersaturatedSupersaturated

When the solvent holds When the solvent holds more more dissolved solutedissolved solute than it normally can at that than it normally can at that temperature.temperature.

Formed when a saturated Formed when a saturated solution is formed at high solution is formed at high temperatures and then temperatures and then cooled slowly.cooled slowly.

SolubilitySolubilitySATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

concentration

Solubility CurvesSolubility Curves Solubility Curves show:Solubility Curves show:

maximum grams of solute that will maximum grams of solute that will dissolve in 100 g of solvent at a dissolve in 100 g of solvent at a given temperaturegiven temperature

varies with temperaturevaries with temperature based on a saturated solutionbased on a saturated solution

SolubilitySolubility Solubility CurveSolubility Curve

shows how shows how temperature temperature affects the affects the solubility of a solubility of a substance.substance.

Solid SolubilitySolid Solubility SolidsSolids are more soluble at... are more soluble at...

high temperatureshigh temperatures

Gas SolubilityGas Solubility Gases are more soluble at...Gases are more soluble at...

low temperatures &low temperatures & high pressures (Henry’s Law).high pressures (Henry’s Law). EXEX: nitrogen narcosis, the “bends,” soda: nitrogen narcosis, the “bends,” soda

Solubility CurveSolubility Curve

Things to rememberThings to remember The graph is set in The graph is set in 100 mL or 100 100 mL or 100

gramsgrams of water. of water. The line represents the The line represents the saturation saturation

pointpoint at that temperature.at that temperature. Anything Anything above the lineabove the line (at that (at that

temp) is temp) is supersaturatedsupersaturated Anything Anything below the linebelow the line (at that (at that

temp) is temp) is unsaturated.unsaturated.

ExampleExample

What amount of NaCl would make a What amount of NaCl would make a saturated solution in 100 mL of water at saturated solution in 100 mL of water at 808000C?C?Just look it up on the graph.Just look it up on the graph.

Answer : Answer : 40 grams40 grams GRAPH

What if it is not What if it is not 100 mL or 100 grams100 mL or 100 grams of of water?water? Set up a proportion:Set up a proportion:

solid solid solidsolid ==

liquidliquid liquidliquid

From graph From

problem

Always

100 mL

This will

be x

ExampleExample

What amount of KNOWhat amount of KNO33 would make a would make a saturated solution in 177mL of water at saturated solution in 177mL of water at 505000C?C?

80 g80 g xx==

100mL100mL 177mL 177mL== 141.6 g 141.6 g GRAPH

What if there is no amount of water given?What if there is no amount of water given? Set up a proportion:Set up a proportion:

solid solid solidsolid ==

liquidliquid liquidliquid

From graph

From problem

Always

100 mLThis will be x

ExampleExample What amount of water at 20What amount of water at 2000C would make a C would make a

saturated solution with 63g of KNOsaturated solution with 63g of KNO33??

30 g30 g 63 g63 g ==

100mL 100mL X X

== 210 mL 210 mL GRAPH

Precipitation Reactions:Precipitation Reactions:What are they?What are they?

Type of Type of double replacementdouble replacement reaction. reaction. Two solutions of ionic compounds are mixedTwo solutions of ionic compounds are mixed One of the products of the reaction is an One of the products of the reaction is an

insoluble salt called a insoluble salt called a precipitateprecipitate (chunky (chunky milk)milk)

Use Use solubility rulessolubility rules to determine the to determine the precipitateprecipitate..

Solubility RulesSolubility RulesSolubility Solubility (in water)(in water)

CompoundsCompounds ExceptionsExceptions

SolubleSoluble Alkali metal (Group 1) saltsAlkali metal (Group 1) salts nonenoneAmmonium salts (NHAmmonium salts (NH44

++)) nonenone

Acetates (CAcetates (C22HH33OO22 - -)) nonenone

Nitrates (NONitrates (NO33 - -)) nonenone

Chlorides (Cl Chlorides (Cl --), Bromides (Br ), Bromides (Br --), ), Iodides (I Iodides (I --))

Compounds of Ag, Hg, and PbCompounds of Ag, Hg, and Pb

Sulfates (SOSulfates (SO44 2- 2-)) Compounds of Sr, Ba, Hg, and Compounds of Sr, Ba, Hg, and

PbPb********** ****************************************************** ******************************************************InsolubleInsoluble Carbonates (COCarbonates (CO33

2- 2-), Phosphates ), Phosphates (PO(PO44

3- 3-), Sulfites (SO), Sulfites (SO33 2- 2-), ),

Chromates (CrOChromates (CrO442-2-))

Compounds of Alkali metal Compounds of Alkali metal (Group 1)(Group 1) and NHand NH44

++

Sulfides (SSulfides (S 2- 2-), Hydroxides (OH), Hydroxides (OH - -)) Compounds of Alkali metal Compounds of Alkali metal (Group 1)(Group 1) and NHand NH44

+, +, Ca, Sr, Ba Ca, Sr, Ba

Example using chartExample using chart

Pb(OH)Pb(OH)22

NHNH44ClCl

KK22SOSO44

BaBa33(PO(PO44))22

Insoluble

Soluble

Soluble

InsolubleRULES

How to use it.How to use it. Write the products for the double Write the products for the double

replacement reactions replacement reactions and balanceand balance.. Then, using the solubility rules Then, using the solubility rules

identify the identify the precipitate by a subscript (s)precipitate by a subscript (s) for solid (insoluble in water). for solid (insoluble in water).

Identify the Identify the soluble compounds by soluble compounds by marking them with a subscript (aq)marking them with a subscript (aq) for for aqueous (soluble in water)aqueous (soluble in water)..

ExampleExample

Ag(NOAg(NO33))22 + LiCl + LiCl

Ag(NOAg(NO33))22 + LiCl + LiCl

Ag(NOAg(NO33))22 + 2 LiCl + 2 LiCl AgCl AgCl22 + 2 LiNO + 2 LiNO33

AgCl2+ LiNO3

+2 -1-1 +1

s aqaq aq

RULES

ConcentrationConcentration The amount of solute in The amount of solute in

a solution.a solution. Describing Describing

ConcentrationConcentration % by mass% by mass - -

medicated creamsmedicated creams % by volume% by volume - -

rubbing alcoholrubbing alcohol Molarity and Molarity and

MolalityMolality - used by - used by chemistschemists

B. MolarityB. Molarity

solvent of literssolute of moles(M)molarity

solvent onlysolvent only

1000mL = 1 L 1000mL = 1 L

MolarityMolarity Find the Molarity of a solution containing .5 Find the Molarity of a solution containing .5

mol of glucose in 2 L of water. mol of glucose in 2 L of water.

= = .25 M.25 M

GIVEN:M = ?Mol = .5 molV = 2 L

WORK:M= mol solute/ liters solvent

M= .5 mol

2 L

2211 VMVM

DilutionDilution

Preparation of a desired solution by Preparation of a desired solution by adding water to a concentrated solution.adding water to a concentrated solution.

Moles of solute remain the same.Moles of solute remain the same.

DilutionDilution What volume of 15.8What volume of 15.8MM HNO HNO33 is required to make 250 mL of is required to make 250 mL of

a 6.0a 6.0MM solution? solution?

GIVEN:M1 = 15.8MV1 = ?

M2 = 6.0MV2 = 250 mL

WORK:M1 V1 = M2 V2

(15.8M) V1 = (6.0M)(250mL)

V1 = 95 mL of 15.8M HNO3