VocabularyVocabularyIn In SOLUTIONSOLUTION we need to define the - we need to define the -

SOLVENT SOLVENT the component whose physical the component whose physical state is preserved when solution formsstate is preserved when solution forms

SOLUTE SOLUTE the other solution componentthe other solution componentThe The CONCENTRATION CONCENTRATION is most often is most often

expressed by chemists as expressed by chemists as MOLARITY. MOLARITY. Other common expressions of Other common expressions of concentration are w/w, vol/vol, and concentration are w/w, vol/vol, and normality.normality.

mL

mmolL

molessolution of liters ofnumber

solute of moles ofnumber molarity

M

M

1.0 L of water was 1.0 L of water was used to make 1.0 used to make 1.0

L of solution. L of solution. Notice the water Notice the water

left over.left over.

CCR, page 206

PROBLEM: Dissolve 5.00 g of NiClPROBLEM: Dissolve 5.00 g of NiCl22•6 H•6 H22O in enough O in enough

water to make 250 mL of solution. Calculate molarity of water to make 250 mL of solution. Calculate molarity of the solution and the concentration of each of the ions.the solution and the concentration of each of the ions.

Problem: What mass of oxalic acid, HProblem: What mass of oxalic acid, H22CC22OO44, is required , is required

to make 250. mL of a 0.0500 M solution?to make 250. mL of a 0.0500 M solution?

PROBLEM: You have 50.0 mL of 3.0 M NaOH and PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you do?you want 0.50 M NaOH. What do you do?

• Zinc reacts with acids Zinc reacts with acids to produce Hto produce H22 gas. gas.

• Have 10.0 g of ZnHave 10.0 g of Zn• What volume of 2.50 What volume of 2.50

M HCl is needed to M HCl is needed to convert the Zn convert the Zn completely?completely?

SOLUTION STOICHIOMETRYSOLUTION STOICHIOMETRYSection 5.10Section 5.10

Zinc reacts with acids to produce HZinc reacts with acids to produce H22 gas. If you have 10.0 g of gas. If you have 10.0 g of

Zn, what volume of 2.50 M HCl is needed to convert the Zn Zn, what volume of 2.50 M HCl is needed to convert the Zn completely?completely?

Non-ElectrolytesNon-Electrolytes – – they dissolve, but won’t conduct they dissolve, but won’t conduct electricity. These are generally polar solids capable of forming electricity. These are generally polar solids capable of forming hydrogen bondshydrogen bonds

– Sugar, ethanol, ethylene glycolSugar, ethanol, ethylene glycol

Strong ElectrolytesStrong Electrolytes – – Completely dissociates, conducts Completely dissociates, conducts electricity well – most ionic solids and strong acidselectricity well – most ionic solids and strong acids

Weak ElectrolytesWeak Electrolytes – – Dissolve, ionize to a small extent, Dissolve, ionize to a small extent, conducts electricity weakly. Weak acids, such as Acetic acid, conducts electricity weakly. Weak acids, such as Acetic acid, ionize only to a small extent, so it are a ionize only to a small extent, so it are a weak electrolyte.weak electrolyte.

CHCH33COCO22HH(aq)(aq) → CH → CH33COCO22--(aq)(aq) +H +H++

(aq)(aq)

Aqueous SolutionsAqueous Solutions

Water Solubility of Ionic CompoundsWater Solubility of Ionic CompoundsIf one ion from the “Soluble If one ion from the “Soluble Compound” list is present in a Compound” list is present in a compound, the compound is compound, the compound is water soluble.water soluble.

There are three ways to write reactions in aqueous solutions.

Molecular equation:Molecular equation: Show all reactants & products in molecular or ionic form

(s)(aq)4(aq)4(s) Cu + ZnSO CuSO + Zn

Total ionic equation: Total ionic equation: Show the ions and molecules as they exist in solution

Net ionic equation:Net ionic equation: Shows ions that participate in reaction and removes spectator ions. Spectator ions do not participate in the reaction.

(s)-2aq4

2aq

-2aq4

2aq(s) Cu +SO+ ZnSO+ Cu+Zn

(s)2aq

2aq(s) Cu + ZnCu + Zn

Net Ionic EquationsNet Ionic EquationsMgMg(s)(s)+ 2HCl+ 2HCl(aq)(aq)→ H→ H2(g) 2(g) + MgCl+ MgCl2(aq)2(aq)

The molecular formula above can be written as the total ionic The molecular formula above can be written as the total ionic formulaformula

MgMg(s)(s)+ 2H+ 2H++(aq)(aq)+ 2Cl+ 2Cl--

(aq)(aq)→ H→ H2(g)2(g)+ Mg+ Mg2+2+(aq)(aq)+ 2Cl+ 2Cl--

(aq)(aq)

The two ClThe two Cl-- ions are ions are SPECTATOR IONSSPECTATOR IONS — they do not — they do not participate. Could have used NOparticipate. Could have used NO3-3- for the spectator ion as salts of for the spectator ion as salts of nitrates are all soluble.nitrates are all soluble.

By leaving out the spectator ions out you get the net ionic reactionBy leaving out the spectator ions out you get the net ionic reaction

MgMg(s)(s) + 2 H + 2 H++(aq)(aq) ---> H ---> H2(g)2(g) + Mg + Mg2+2+

(aq)(aq)

HNOHNO33

A Brönsted-Lowry Acid → HA Brönsted-Lowry Acid → H++ in water in waterACIDS ACIDS Table 5.2Table 5.2

StrongStrong Brönsted-Lowry acids are strong electrolytes Brönsted-Lowry acids are strong electrolytesHClHCl hydrochlorichydrochloric

HH22SOSO44 sulfuricsulfuric

HClOHClO44 perchloricperchloric

HNOHNO33 nitricnitric

Weak Weak Brönsted-Lowry Brönsted-Lowry acids are weak electrolytesacids are weak electrolytes

CHCH33COCO22H acetic acid (CHH acetic acid (CH33COOH) COOH)

HH22COCO3 3 carbonic acidcarbonic acid

HH33POPO4 4 phosphoric acidphosphoric acid

HF HF hydrofluoric acidhydrofluoric acid

Acetic acid

Carbonic Acid

Ammonia, NHAmmonia, NH33 a an Important weak Base

Brönsted-LowryBrönsted-Lowry Base → OHBase → OH-- in water in water

BASESBASES Table 5.2Table 5.2

NaOH(aq) → Na+(aq) + OH-(aq)NaOH(aq) → Na+(aq) + OH-(aq)

NaOH is a strong baseNaOH is a strong base

ACIDSACIDSNonmetal oxides can be acidsNonmetal oxides can be acids

COCO2(aq)2(aq) + H + H22OO(l)(l) → H → H22COCO3(aq)3(aq)

SOSO3(aq)3(aq) + H + H22OO(l)(l) → H → H22SOSO4(aq)4(aq)

NONO2(aq)2(aq) + H + H22OO(l)(l) → HNO → HNO3(aq)3(aq)

Acid Rain is an example of nonmetal oxides behaving Acid Rain is an example of nonmetal oxides behaving as acids. This process can result from burning coal and as acids. This process can result from burning coal and oil.oil.

Metal oxides can be basesMetal oxides can be basesCaOCaO(s)(s)+H+H22OO(l)(l) → Ca(OH) → Ca(OH)2(aq)2(aq)

CaO in water. Phenolphthalein indicator shows a of calcium oxide solution is basic.

BASESBASES

You should know the You should know the strong acids & basesstrong acids & bases

A brief history of Acid-Base Identification Systems

System Acid (HCl) Base (NaOH)

Arrhenius

Brönsted-LowryLewis

pH, a Concentration ScalepH, a Concentration ScalepH: a way to express acidity -- the concentration of HpH: a way to express acidity -- the concentration of H++ in in

solution.solution.

Low pH: high [HLow pH: high [H++]] High pH: low [HHigh pH: low [H++]]

Acidic solutionAcidic solution pH < 7pH < 7 Neutral Neutral pH = 7pH = 7 Basic solution Basic solution pH > 7pH > 7

Acidic solutionAcidic solution pH < 7pH < 7 Neutral Neutral pH = 7pH = 7 Basic solution Basic solution pH > 7pH > 7

The pH ScaleThe pH Scale

pH pH = log (1/ [H= log (1/ [H++]) = - log [H]) = - log [H++]]In a In a neutralneutral solution, solution, [H[H++] = ] =

[OH[OH--] = 1.00 x 10] = 1.00 x 10-7-7 M at 25 M at 25 ooCC

pH = - log [HpH = - log [H++] = ] =

If the [HIf the [H++] of soda is 1.6 x 10] of soda is 1.6 x 10-3-3 M, the pH is ____. M, the pH is ____.

If the pH of Coke is 3.12, it is _____.If the pH of Coke is 3.12, it is _____.

ACID-BASE REACTIONSACID-BASE REACTIONSTitrationsTitrations

HH22CC22OO4(aq) 4(aq) + 2 NaOH + 2 NaOH(aq)(aq) → Na → Na22CC22OO4(aq)4(aq) + 2 H + 2 H22OO(l)(l)

acidacid basebase

Carry out this reaction using a Carry out this reaction using a TITRATIONTITRATION..

Oxalic acid,Oxalic acid,

HH22CC22OO44

TitrationTitration1. Add solution from the buret.1. Add solution from the buret.2. Reagent (base) reacts with 2. Reagent (base) reacts with

compound (acid) in solution compound (acid) in solution in the flask.in the flask.

3. Indicator shows when exact 3. Indicator shows when exact stoichiometric reaction has stoichiometric reaction has occurred.occurred.

4. Net ionic equation4. Net ionic equation HH++ + OH + OH-- --> H --> H22OO5. At equivalence point 5. At equivalence point moles Hmoles H++ = moles OH = moles OH--

PROBLEM: Standardize a solution of NaOH — i.e., accurately PROBLEM: Standardize a solution of NaOH — i.e., accurately determine its concentration. determine its concentration. 1.065 g of H2C2O4 (oxalic acid) requires 35.62 mL of NaOH for titration to an equivalence point. What is the concentration of the NaOH?

PROBLEM : Use standardized NaOH to determine the amount PROBLEM : Use standardized NaOH to determine the amount

of an acid in an unknown. Apples contain malic acid, Cof an acid in an unknown. Apples contain malic acid, C44HH66OO55. .

76.80 g of apple requires 34.56 mL of 0.663 M NaOH for 76.80 g of apple requires 34.56 mL of 0.663 M NaOH for

titration. What is weight % of malic acid? titration. What is weight % of malic acid?

CC44HH66OO5(aq)5(aq) + 2NaOH + 2NaOH(aq)(aq) → Na → Na22CC44HH44OO5(aq)5(aq) + 2 H + 2 H22OO(l)(l)

Types of Reactions:1. Combination Reactions

• More than one reactant, one product

2. Decomposition Reactions• Single reactant, more than one product

3. Displacement Reactions• One element displaces another from a compound

4. Redox – Oxidation Reduction Reactions• Oxidation numbers of some elements change; at least one element

must increase and one must decrease in oxidation number.

5. Metathesis Reactions - Exchange Reactions • Precipitation: products include an insoluble substance which

precipitates from solution as a solid• Acid-base neutralization: product is a salt and water• Gas formation – primarily the reaction of metal carbonates

OXIDATION NUMBERSOXIDATION NUMBERS

NHNH33

ClOClO--

HH33POPO44

MnOMnO44- -

CrCr22OO772-2-

Recognizing a Redox ReactionRecognizing a Redox Reaction

2 Al2 Al(s)(s) + 3 Cu + 3 Cu2+2+(aq)(aq) → 2 Al → 2 Al3+3+

(aq)(aq) + 3 Cu + 3 Cu(s)(s)

Oxidation-Reduction ReactionsOxidation-Reduction ReactionsThermite reactionThermite reaction

FeFe22OO3(s)3(s) + 2Al + 2Al(s)(s) → 2 Fe → 2 Fe(s)(s) + Al + Al22OO3(s)3(s)

2Al2Al(s)(s) + 3Cu + 3Cu2+2+(aq)(aq) → 2Al → 2Al3+3+

(aq)(aq)+ 3Cu+ 3Cu(s)(s)

2 H2 H2(g)2(g) + O + O2(g)2(g) → 2H → 2H22OO(l)(l)

In all reactions if something has been oxidized then In all reactions if something has been oxidized then something has also been reduced.something has also been reduced.Redox reactions are characterized byRedox reactions are characterized by ELECTRON TRANSFER ELECTRON TRANSFER between an electron donor and electron acceptor.between an electron donor and electron acceptor.Transfer leads toTransfer leads to 1. 1. increase in oxidation numberincrease in oxidation number of some element = of some element = OXIDATIONOXIDATION2.2.decrease in oxidation numberdecrease in oxidation number of some element = of some element = REDUCTIONREDUCTION

Chemical Reactions in WaterChemical Reactions in WaterMetathesisMetathesis

• EXCHANGE REACTIONSEXCHANGE REACTIONS

AX + BY AY + BX

PrecipitationPrecipitationPb(NOPb(NO33))2(aq)2(aq) + 2 KI + 2 KI(aq) (aq) → PbI→ PbI2(s)2(s) + 2KNO + 2KNO3(aq)3(aq)

Pb2+(aq) + 2 I-(aq) → PbI2(s)Pb2+(aq) + 2 I-(aq) → PbI2(s)Neutralization:Neutralization:

NaOHNaOH(aq)(aq) + HCl + HCl(aq)(aq)→ NaCl→ NaCl(aq)(aq)+ H+ H22OO(l)(l)

OHOH--(aq)(aq) + H + H++

(aq)(aq) → H→ H22OO(lq)(lq)

Gas FormationGas FormationMgCOMgCO3(s)3(s)+ 2+ 2HCl(aq)(aq) → 2Mg(Cl) → 2Mg(Cl)2(aq)2(aq)+ H+ H22OO(l)(l) + CO2(g)

The anions exchange places between The anions exchange places between cations.cations.