SolutionsSolutions

SolutionsSolutionsWhat are solutions?What are solutions? a homogeneous mixture of two or more substances; a homogeneous mixture of two or more substances;

the different substances the different substances cannotcannot be mechanically be mechanically separated or seen. separated or seen.

A A solutionsolution may be a solid (stainless steel), a liquid may be a solid (stainless steel), a liquid (iced tea) or a gas (the air we breathe).(iced tea) or a gas (the air we breathe).

Solvent:Solvent: the substance that is present the substance that is present in the largest amount - usually in the largest amount - usually determines the phase of the solutiondetermines the phase of the solution

Solute:Solute: the substance present in the the substance present in the smallest amount – what is dissolved smallest amount – what is dissolved in the solvent.in the solvent.

We will deal mainly with solutions where water is the We will deal mainly with solutions where water is the solvent (aqueous solutions)solvent (aqueous solutions)

Why is water considered to be the universal solvent?Why is water considered to be the universal solvent? Water is able to dissolve many types of solutes.Water is able to dissolve many types of solutes.

Water is a polar moleculeWater is a polar molecule The negative oxygen The negative oxygen

attracts positive ions, and attracts positive ions, and they hydrogen ends they hydrogen ends attracts the negative ions attracts the negative ions of ionic compoundsof ionic compounds

What about molecular What about molecular compounds like sugar compounds like sugar (C(C1212HH2222OO1111)?)?

http://programs.northlandcollege.edu/biology/Biology1111/animations/dissolve.htmlhttp://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

ElectrolyteElectrolyte:: a substance that conducts a substance that conducts electricity when dissolved in water. electricity when dissolved in water. AcidsAcids, , basesbases and and soluble ionic solutionssoluble ionic solutions are are

electrolytes because they dissolve into electrolytes because they dissolve into ions.ions. Insoluble ionic compounds are very Insoluble ionic compounds are very weak electrolytesweak electrolytes

Non-electrolyte:Non-electrolyte: a substance that a substance that does not conduct electricity when does not conduct electricity when dissolved in water.dissolved in water. Molecular compoundsMolecular compounds are non-electrolytes are non-electrolytes

because they do not dissolve into ionsbecause they do not dissolve into ions

Four different types of solutionsFour different types of solutionsNeutral Neutral molecularmolecular

Neutral Neutral ionicionic

AcidAcid basebase

Solutions of Solutions of compounds that compounds that are composed are composed of non-metals of non-metals only. only.

Solutions of Solutions of compounds that compounds that are composed are composed of metals of metals combined with combined with non-metals non-metals

Solutions of Solutions of compounds that compounds that produce produce hydrogen ions. hydrogen ions.

Solutions of Solutions of compounds that compounds that produce produce hydroxide ions hydroxide ions

CC1212HH2222OO11(aq)11(aq) NaCl(aq) NaCl(aq) HCl(aq) HCl(aq) KOH(aq) KOH(aq)

CHCH33OH(aq)OH(aq) CaBrCaBr22(aq) (aq) HH22SOSO44(aq) (aq) Mg(OH)Mg(OH)2(aq2(aq

No effect No effect on litmuson litmus

No effect No effect on litmuson litmus

Turns Turns litmus redlitmus red

Turns Turns litmus bluelitmus blue

1. Neutral Molecular 1. Neutral Molecular Solutions containing molecular compounds (non metals Solutions containing molecular compounds (non metals

sharing electrons)sharing electrons) No ions form in solution, therefore do NOT conduct No ions form in solution, therefore do NOT conduct

electricity (non-electrolytes)electricity (non-electrolytes) No change in color with litmus paperNo change in color with litmus paper Form colorless solutionsForm colorless solutions Examples: Examples:

2. Neutral Ionic 2. Neutral Ionic Dissociate in water to form positive and negative ions Dissociate in water to form positive and negative ions Conduct electricity (electrolytes)Conduct electricity (electrolytes) No change in color with litmus paperNo change in color with litmus paper Form colorless and colorful solutions Form colorless and colorful solutions Examples:Examples:

3. Acidic Solutions3. Acidic Solutions Form when an acid is dissolved in waterForm when an acid is dissolved in water acid dissociates into positive hydrogen ions and negative ionsacid dissociates into positive hydrogen ions and negative ions The concentration of HThe concentration of H++ ions in solution indicate the pH ions in solution indicate the pH

(strength of acid) (strength of acid) Electrolytes (conduct electricity)Electrolytes (conduct electricity) Turn blue litmus paper redTurn blue litmus paper red

4. Basic Solutions4. Basic Solutions Bases - presence hydroxide ions (OHBases - presence hydroxide ions (OH--)) ElectrolytesElectrolytes Turn red litmus paper blueTurn red litmus paper blue Conc. of OH- ions indicates pH levelConc. of OH- ions indicates pH level Examples Examples

Acids and Bases DefinedAcids and Bases Defined

Acids are empirically defined as substances that:Acids are empirically defined as substances that: Taste sourTaste sour Conduct electricity (they are electrolytes)Conduct electricity (they are electrolytes) React with metals to produce hydrogen gasReact with metals to produce hydrogen gas Turn blue litmus paper redTurn blue litmus paper red Their pH ranges between 0 and 7Their pH ranges between 0 and 7

Bases are empirically defined as substances Bases are empirically defined as substances that:that:

Taste bitterTaste bitter Conduct electricity (they are electrolytes)Conduct electricity (they are electrolytes) Feel soapy or slipperyFeel soapy or slippery Turn red litmus paper blueTurn red litmus paper blue Their pH ranges between 7 and 14Their pH ranges between 7 and 14

Testing Acids, Bases and Ionic Testing Acids, Bases and Ionic SubstancesSubstances

To distinguish between acids, bases and To distinguish between acids, bases and ionic substances a few simple ionic substances a few simple diagnostic diagnostic teststests can be used. can be used.

1)1) The litmus testThe litmus test - used primarily to distinguish - used primarily to distinguish acids from bases. acids from bases.

2)2) The conductivity testThe conductivity test – – used to determine if a used to determine if a solution is ionic, acidic, basic, or if the solution is solution is ionic, acidic, basic, or if the solution is molecular.molecular.

Litmus Litmus PaperPaper

ConductivityConductivity Compound in Compound in SolutionSolution

11 Red Red red red YesYes

22 Blue Blue red red YesYes

33 Blue Blue blue blue NoNo

44 Red Red blue blue YesYes

A - calcium carbonateB - sulfurous acidC - potassium hydroxideD - sucrose

1.1. NaOHNaOH 5. CH5. CH33OHOH2.2. HClHCl 6. NaCl6. NaCl3.3. AgAg22OO 7. CH7. CH33COOHCOOH4.4. CHCH44

CompoundCompound Red litmusRed litmus Blue Blue litmuslitmus

Conduct ?Conduct ? LayersLayers Type of Type of compoundcompound

RedRed RedRed YesYes nono

Red Red BlueBlue Yes Yes nono

RedRed BlueBlue NoNo YesYes

Red Red BlueBlue NoNo NoNo

BlueBlue BlueBlue YesYes nono

RedRed RedRed WeaklyWeakly NoNo

RedRed BlueBlue WeaklyWeakly yesyes

Substances Present in Substances Present in WaterWater

Solutions made by dissolving solutes in water Solutions made by dissolving solutes in water are called are called aqueous solutionsaqueous solutions. .

If the temperature of the solution rises as a If the temperature of the solution rises as a solute is dissolved, the reaction is said to be solute is dissolved, the reaction is said to be exothermicexothermic; e; energy is released to the solvent nergy is released to the solvent ** energy is a product in the chemical reaction. energy is a product in the chemical reaction.

If the temperature of the solution decreases as If the temperature of the solution decreases as a solute is dissolved, the reaction is said to be a solute is dissolved, the reaction is said to be endothermicendothermic;; energy is absorbed in the energy is absorbed in the solvent. solvent. ** energy is a reactant in the chemical reaction. energy is a reactant in the chemical reaction.

DissociationDissociation, Ionization & Separation, Ionization & Separation

We use our We use our solubility solubility table to determine if table to determine if something dissociates or notsomething dissociates or not

DissociationDissociation:: the separation of ions from an the separation of ions from an ionic ionic compoundcompound when it dissolves in water. when it dissolves in water.

Ex. If magnesium chloride is dissolved in water, it will Ex. If magnesium chloride is dissolved in water, it will form magnesium ions and chloride ions. form magnesium ions and chloride ions.

Mg(Cl)Mg(Cl)2(s)2(s) Mg Mg2+2+(aq)(aq) + 2Cl + 2Cl--(aq)(aq)

Please note that the equation must be balanced Please note that the equation must be balanced the same as any other equation. Also note that the same as any other equation. Also note that the charges on both sides of the equation are the charges on both sides of the equation are balanced. balanced.

Ex. KEx. K22SOSO4(s)4(s) 2K 2K++(aq)(aq) + SO + SO44

2-2-(aq)(aq)

Ca(NOCa(NO33))2(s)2(s) Ca Ca2+2+(aq)(aq) + 2NO + 2NO33

--(aq)(aq)

If the ionic compound does not dissolve in water, If the ionic compound does not dissolve in water, it will remain as an ionic compound in water. it will remain as an ionic compound in water. Ex. Ex. AgBrAgBr(s)(s) AgBr AgBr(s)(s)

Molecular compounds do not dissociate into Molecular compounds do not dissociate into respective ions in water. They respective ions in water. They dissolvedissolve in in solution. solution. Ex. Ex. CC66HH1212OO6(s)6(s) C C66HH1212OO6(aq)6(aq)

The formation of charged ions from neutral atoms The formation of charged ions from neutral atoms by the action of the solvent is called by the action of the solvent is called ionizationionization. . Acids undergo ionization in aqueous solution. Acids undergo ionization in aqueous solution.

• When acids When acids are notare not dissolved in water, they are molecular dissolved in water, they are molecular compounds (two nonmetals). compounds (two nonmetals).

• When acids When acids are are dissolved in water they conduct electricity. dissolved in water they conduct electricity. Therefore, we assume that they ionize in solution; they form Therefore, we assume that they ionize in solution; they form ions once they have dissolved in water. ions once they have dissolved in water.

• Ex.Ex. HCl(g) HCl(g) H H++(aq) + Cl(aq) + Cl--(aq)(aq)

Qualitative Analysis of Ions in Qualitative Analysis of Ions in SolutionsSolutions

Flame Test:Flame Test: Some ions impart specific colours when subjected Some ions impart specific colours when subjected

to flameto flame

Solution Colour:Solution Colour: Some ions create specific colours when in solution.Some ions create specific colours when in solution.

Precipitates:Precipitates: By understanding the solubility table, we can By understanding the solubility table, we can

determine what ions are in solution by whether or determine what ions are in solution by whether or not a precipitate is formed.not a precipitate is formed.

ConcentrationConcentration There are many ways to measure There are many ways to measure

concentration. 3 common ways:concentration. 3 common ways:1)1) Percentage of solute compared to Percentage of solute compared to

solvent by volume solvent by volume (%v/v)(%v/v)2)2) Moles of solute per unit volume of Moles of solute per unit volume of

solution solution (mol/L)(mol/L). The units for . The units for concentration are usually written asconcentration are usually written as mol/Lmol/L. .

3)3) You will also see ppm – parts per You will also see ppm – parts per million million (mg/L).(mg/L).

Ways to Write Concentration Using Ways to Write Concentration Using PercentsPercents

We can use two methods of representing We can use two methods of representing concentrations based on percentconcentrations based on percent

% by mass (%m/v) or % by volume (%v/v)% by mass (%m/v) or % by volume (%v/v) Simply put the solute is put in a ratio with Simply put the solute is put in a ratio with

100 ml (because percent is out of 100) of 100 ml (because percent is out of 100) of solutionsolution

We will focus on (%v/v)We will focus on (%v/v)

(%v/v) Examples(%v/v) Examples

45 ml of methyl alcohol is mixed with 55 ml of 45 ml of methyl alcohol is mixed with 55 ml of water. What is the % v/v of the solutionwater. What is the % v/v of the solution

45 is the solute, (45 + 55) is the total solution45 is the solute, (45 + 55) is the total solution 45 ml / 100 ml is 45%45 ml / 100 ml is 45% how many grams of NaCl must be added to 25.0 how many grams of NaCl must be added to 25.0

ml of water to prepare a 7.50% solutionml of water to prepare a 7.50% solution 7.5 / 100 = X / 257.5 / 100 = X / 25

=1.875 g=1.875 g

PPMPPM one way of representing solution concentration one way of representing solution concentration

is ppm (parts per million)is ppm (parts per million) simply put its mg / Lsimply put its mg / L 8 mg of solute in 1 L of solution is 8 ppm8 mg of solute in 1 L of solution is 8 ppm Example: some water has 6.3 X 10Example: some water has 6.3 X 10-3-3 g of lead g of lead

per 375 mL of solution. What is the ppm per 375 mL of solution. What is the ppm concentration?concentration?

6.3 X 106.3 X 10-3-3 g / 375 mL g / 375 mL convert g to mg and mL to Lconvert g to mg and mL to L so 6.3 mg / .375 L = X / 1Lso 6.3 mg / .375 L = X / 1L

=16.8 ppm=16.8 ppm

Concentration in Concentration in SolutionSolution Several ways to indicate the strength or Several ways to indicate the strength or concentrationconcentration

of a solution. of a solution. Generally expressed as the number of moles of solute Generally expressed as the number of moles of solute

dissolved in one liter of solution. dissolved in one liter of solution. Concentration is often referred to as Concentration is often referred to as molaritymolarity ( (MM). ). The symbol for concentration is The symbol for concentration is CC. .

To To calculatecalculate the concentration of a solution, use the the concentration of a solution, use the following formula:following formula:

C = C = nn VV

C = concentration (mol/L)C = concentration (mol/L) n = number of moles (mol)n = number of moles (mol) V = volume (L)V = volume (L)

Molar Concentration ExamplesMolar Concentration Examples

What is the concentration made from What is the concentration made from dissolving 8.0 moles of CuSOdissolving 8.0 moles of CuSO44 in 2.2 litres in 2.2 litres

of waterof water Step 1Step 1

Write down what you know and don’t knowWrite down what you know and don’t know n = 8.0 molsn = 8.0 mols M = 159.62 g/molM = 159.62 g/mol v = 2.2 Lv = 2.2 L

Step 2Step 2 Write down and rearrange your formulaWrite down and rearrange your formula c = n / vc = n / v

Step 3Step 3 Plug in your number and include your unitsPlug in your number and include your units C = (8.0 mols) / 2.2 LC = (8.0 mols) / 2.2 L

= 3.636363636 mol/L= 3.636363636 mol/L SIG DIGSSIG DIGS

= 3.6 mol/L= 3.6 mol/L

More Examples:More Examples: Example 2:Example 2: What is the concentration when 5.2 moles of hydrosulfuric What is the concentration when 5.2 moles of hydrosulfuric

acid are dissolved in 500 mL of water?acid are dissolved in 500 mL of water?

Step one:Step one: Convert volume to liters, mass to moles.Convert volume to liters, mass to moles.

500 mL = 0.500 L500 mL = 0.500 L

Step two:Step two: Calculate concentration.Calculate concentration.

C = 5.2 mol / 0.500 LC = 5.2 mol / 0.500 L = 10 mol/L = 10 mol/L

Concentration and Mass Concentration and Mass CalculationsCalculations

a) To calculate concentration, given the a) To calculate concentration, given the number of moles and the volume, use number of moles and the volume, use factor-analysis or the equation C = n/V.factor-analysis or the equation C = n/V.

b) To calculate the mass of solute required to b) To calculate the mass of solute required to make a solution, given the concentration make a solution, given the concentration and volume, follow these steps:and volume, follow these steps:

1) Calculate the number of moles required 1) Calculate the number of moles required n = C·Vn = C·V

2) Calculate the molar mass of the solute2) Calculate the molar mass of the solute3) Calculate the mass required3) Calculate the mass required

m = n·Mm = n·M

you may have to use both formulas we you may have to use both formulas we know to solve questions:know to solve questions:

m=nM and c=n/vm=nM and c=n/v Example: What is the mass of solute in Example: What is the mass of solute in

4.50L of a 2.4 mol/L solution of HCl ?4.50L of a 2.4 mol/L solution of HCl ?

Solution PreparationSolution PreparationWhen a chemist prepares aWhen a chemist prepares a standard solutionstandard solution

from a solid reagent, the following steps from a solid reagent, the following steps should be taken:should be taken:

1)1) Calculate the required mass of solute.Calculate the required mass of solute.2)2) Obtain the required mass of solute in Obtain the required mass of solute in

a clean, dry beaker.a clean, dry beaker.3)3) Dissolve the solute in distilled water Dissolve the solute in distilled water

using about one half of the final using about one half of the final solution volume.solution volume.

4)4) Transfer the solution and all the water Transfer the solution and all the water used to rinse the equipment into a clean used to rinse the equipment into a clean volumetric flask.volumetric flask.

5)5) Add distilled water until the desired Add distilled water until the desired volume is reached.volume is reached.

6)6) Stopper the flask and mix the solution Stopper the flask and mix the solution by inverting the flask several times.by inverting the flask several times.

Dilution CalculationsDilution Calculations The process of decreasing the concentration of a The process of decreasing the concentration of a

solution usually by adding more solvent. solution usually by adding more solvent. During a dilution procedure the addition of water During a dilution procedure the addition of water

changes the volume of the original solution as well as the changes the volume of the original solution as well as the concentration. HOWEVER the original number of moles concentration. HOWEVER the original number of moles remains the same.remains the same.

nnii (before diluting)(before diluting) = n= nff (after diluting)(after diluting)

therefore, therefore, CCi i · V· Vii = C = Cf f · V· Vff

CCii = initial concentration = initial concentration

CCff = final concentration = final concentration

VVii = initial volume = initial volume

VVf f = = final volumefinal volume

Dilution ProblemsDilution Problems

Eg. Water is added to 200mL of a 2.40mol/L of Eg. Water is added to 200mL of a 2.40mol/L of NHNH33 cleaning solution until the final volume is cleaning solution until the final volume is 1.00L. Find the molar concentration of the final 1.00L. Find the molar concentration of the final diluted solution.diluted solution.

0.200L x 2.40mol/L = 1.00L x c0.200L x 2.40mol/L = 1.00L x c= 0.480mol/L= 0.480mol/L

Change a solution of 30 mL of 0.430 mol/L of Change a solution of 30 mL of 0.430 mol/L of KIO solution to the solutions of the following KIO solution to the solutions of the following volumes:volumes:

40mL, 25mL, 180mL 40mL, 25mL, 180mL

More ExamplesMore Examples

Example 3:Example 3:

What is the concentration of a solution if 30.0 mL What is the concentration of a solution if 30.0 mL of 4.00 mol/L NaBr(aq) was diluted to a new of 4.00 mol/L NaBr(aq) was diluted to a new volume of 1.50 L?volume of 1.50 L?

Example 4:Example 4:

What is the original concentration of a stock What is the original concentration of a stock solution if 40 mL of the stock solution was used solution if 40 mL of the stock solution was used to make 2.00 L of a 0.0100 mol/L solution? to make 2.00 L of a 0.0100 mol/L solution?

Diluting the SolutionDiluting the SolutionOnce a standard solution has been prepared, a Once a standard solution has been prepared, a

chemist may wish to chemist may wish to dilutedilute the solution the solution further. To do this, please follow these steps:further. To do this, please follow these steps:

1)1) Calculate the volume of standard solution Calculate the volume of standard solution required to make the diluted solution.required to make the diluted solution.

2)2) Add about one half of the final volume of Add about one half of the final volume of distilled water to the volumetric flask.distilled water to the volumetric flask.

3)3) Measure the required volume of Measure the required volume of stock solution using a pipet (see stock solution using a pipet (see page 532 of your textbook).page 532 of your textbook).

4)4) Transfer the stock solution to Transfer the stock solution to the volumetric flask.the volumetric flask.

5)5) Add distilled water to the bottom Add distilled water to the bottom of the calibration line.of the calibration line.

6)6) Stopper and invert the flask several Stopper and invert the flask several times to mix the solution.times to mix the solution.

Neutralization ReactionsNeutralization Reactions

A A neutralizationneutralization reaction is a double reaction is a double replacement reaction where an acid reacts replacement reaction where an acid reacts with a base to produce water and a neutral with a base to produce water and a neutral substance. substance.

Following are a few examples of Following are a few examples of neutralization reactions:neutralization reactions:

HH22COCO3(aq)3(aq) + 2NaOH + 2NaOH(aq)(aq) NaNa22COCO3(aq)3(aq) + 2HOH + 2HOH(l)(l)

acidacid base base neutralneutral water water

2HCl2HCl(aq)(aq) + + Mg(OH)Mg(OH)2(aq) 2(aq) MgClMgCl2(aq)2(aq) + 2HOH + 2HOH(l)(l)

acidacid base base neutralneutral water water

PrecipitatesPrecipitates

Sometimes when two soluble Sometimes when two soluble ionic compounds are mixed, ionic compounds are mixed, an insoluble product is formed. an insoluble product is formed.

This insoluble product forms a This insoluble product forms a solid, which is known as a solid, which is known as a precipitateprecipitate. .

The reaction to form a The reaction to form a precipitate is a precipitate is a double double replacement reactionreplacement reaction. .