Chem Lab 2Chem Lab 2

SolutionsSolutions

Lab 2.1Lab 2.1

Adding Liquids to WaterAdding Liquids to Water

Lab Procedures- Lab Procedures- Behavior of DropsBehavior of Drops

WaterWater Drops are high and Drops are high and

roundround Drops stay together Drops stay together

when draggedwhen dragged Wet toothpick pulls Wet toothpick pulls

drop upwarddrop upward Many more drops can Many more drops can

be added to a penny be added to a penny before falling off.before falling off.

PropanolPropanol Drops are flatDrops are flat Drops leave a trail Drops leave a trail

when draggedwhen dragged Less drops can be Less drops can be

added to a penny added to a penny before falling off.before falling off.

Attractions between Attractions between MoleculesMolecules

Water molecules are more attracted to Water molecules are more attracted to each other than alcohol moleculeseach other than alcohol molecules

Dipole-dipole attractions keep the Dipole-dipole attractions keep the molecules together as the drop is molecules together as the drop is dragged or piled upon a penny.dragged or piled upon a penny.

Hydrogen bonds are a stronger version Hydrogen bonds are a stronger version of dipole-dipole attractions when of dipole-dipole attractions when hydrogen atoms are one of the atoms.hydrogen atoms are one of the atoms.

Water vs AlcoholWater vs Alcohol

Water is a polar molecule with two polar Water is a polar molecule with two polar O-H bonds (oxygen pulls harder on O-H bonds (oxygen pulls harder on negative e- resulting a partial negative negative e- resulting a partial negative charge while hydrogen has a partial charge while hydrogen has a partial positive charge)positive charge)

Alcohol has both a polar part and Alcohol has both a polar part and nonpolar part- therefore alcohol nonpolar part- therefore alcohol molecules are less attracted to each molecules are less attracted to each other.other.

Attractions between MoleculesAttractions between Molecules

WaterWater Alcohol Alcohol

Lab Procedures- Lab Procedures- solubilitysolubility

Nonpolar substances Nonpolar substances do not noticeably do not noticeably dissolve in waterdissolve in water OilOil HexaneHexane KeroseneKerosene

A thin stream of liquid A thin stream of liquid did not bend towards did not bend towards a charged roda charged rod

Polar substances Polar substances dissolve in waterdissolve in water PropanolPropanol Ethanoic acidEthanoic acid Hydrochloric acidHydrochloric acid

A thin stream of water A thin stream of water net towards a charged net towards a charged rod. Other polar rod. Other polar liquids bent slightly liquids bent slightly towards charged rod.towards charged rod.

Polar solutes dissolve in polar water.

Dipole-dipole attractions form between the polar molecules. The covalent bonds between atoms remain in tact while the attractions between molecules are broken and formed.

The ethylene glycol molecules move between the water molecules due to the attractions these molecules.

Nonpolar molecules are not attracted to polar water molecules.

Like dissolves Like.

Nonpolar solutes dissolve in nonpolar solvents. Since the induced dipole attractions between the molecules is relatively weak, random mixing is responsible for the dissolving process.

Like dissolves LikeLike dissolves Like

The nonpolar iodine dissolved to a small extent in the water. Weak induced dipole-dipole attractions form between the molecules.

Upon shaking the iodine leaves the water and becomes dissolved in the nonpolar carbon tetrachloride. Weak induced dipole-induced dipole attractions form between the molecules.

Predicting the Predicting the polarity of a bondpolarity of a bond

Use electronegativityUse electronegativity

ElectronegativityElectronegativity

A measure of atom’s pull on electrons A measure of atom’s pull on electrons within a bondwithin a bond

The most electronegative atom is fluorine The most electronegative atom is fluorine with an electronegativity of 4.0with an electronegativity of 4.0

The least electronegative atom is The least electronegative atom is francium with an electronegativity of 0.8.francium with an electronegativity of 0.8.

ElectronegativityElectronegativity

Using Electronegativity to Using Electronegativity to determine the nature of the determine the nature of the bond between atomsbond between atoms

Calculating the difference between the Calculating the difference between the electronegativity (EN) indicates how electronegativity (EN) indicates how much harder one atom is pulling much harder one atom is pulling compared to the other atom.compared to the other atom.

Difference in ENDifference in EN

0.0------0.5------------------------1.9----------0.0------0.5------------------------1.9----------

NonpolarNonpolar PolarPolar Ionic Ionic

Little or no difference in Little or no difference in the electronegativitythe electronegativity

If both atoms exert the same pull, they If both atoms exert the same pull, they share electrons equally. A nonpolar share electrons equally. A nonpolar covalent bond forms between the atoms. covalent bond forms between the atoms. NO OPPOSITELY CHARGED ENDSNO OPPOSITELY CHARGED ENDS are formed.are formed.

If the difference in EN is between 0 – 0.5, If the difference in EN is between 0 – 0.5, NONPOLAR COVALENT BONDSNONPOLAR COVALENT BONDS FORM. FORM.

POLAR COVALENT BONDSPOLAR COVALENT BONDS

If one atom pulls harder than the other, If one atom pulls harder than the other, a difference between 0.5 – 1.9.a difference between 0.5 – 1.9. an unequal sharing of electrons may occuran unequal sharing of electrons may occur

The pair of electrons will spend more The pair of electrons will spend more time at the more electronegative end.time at the more electronegative end.

This end will become partially negative This end will become partially negative and the other end partially positive.and the other end partially positive.

IONIC BONDSIONIC BONDS

One atom pulls so much harder that the One atom pulls so much harder that the atom takes the electron, rather than atom takes the electron, rather than sharing the electron(s)- difference in EN sharing the electron(s)- difference in EN greater than 1.9greater than 1.9

The more electronegative atom gains an The more electronegative atom gains an electron(s) and becomes a negative ion.electron(s) and becomes a negative ion.

The less electronegative atom loses an The less electronegative atom loses an electron(s) and becomes a positive ion.electron(s) and becomes a positive ion.

Attractions between Attractions between moleculesmolecules

Between Between nonpolarnonpolar molecules– weak molecules– weak induced dipole-induced dipole attractionsinduced dipole-induced dipole attractions act between the molecules. There are no act between the molecules. There are no oppositely charged ends, so temporary oppositely charged ends, so temporary dipoles may be induced.dipoles may be induced.

Between Between polarpolar molecules– molecules– dipole-dipole dipole-dipole attractionsattractions act between the molecules. act between the molecules. Oppositely charged ends or dipoles are Oppositely charged ends or dipoles are attracted.attracted.

Dipole-dipole attractions form between oppositely charged ends of different polar molecules

polar molecule

Dipole-dipole attractions form between polar water molecules and polar alcohol molecules. The molecules have moved between each other. The individual molecules remain intact.

METHANOL DISSOLVES IN WATER.Notice: The covalent bonds between the atoms remain intact the molecules have simply moved between each other.

Dipole-dipole attractions between ethanoic acid molecules. Also known as glacial acetic acid.

Polarity and SolubilityPolarity and Solubility

Oil in water

Induced dipole – Induced dipole – Induced dipole Induced dipole AttractionsAttractions

Temporary shifts in electron density lead to temporary dipoles

Packing peanuts will dissolve in acetone

Nonpolar Nonpolar

Due to random motion and and mixing (entropy driven- increasing disorder) the molecules mix between each other. Since there is little attraction between any of the molecules, they simple mix

Weak induced dipole – induced dipole attractions

Styrofoam in acetone

Styrofoam in water

Is styrofoam polar or nonpolar?

Dipole-induced dipole Dipole-induced dipole AttractionsAttractions

Polar molecule

Nonpolar molecule

Nonpolar oxygen Nonpolar oxygen dissolves in water to a dissolves in water to a small extentsmall extent

Fish breath oxygen molecules that are Fish breath oxygen molecules that are dissolved in the waterdissolved in the water

Weak attractions form between oxygen Weak attractions form between oxygen molecules that allow some oxygen to molecules that allow some oxygen to dissolve in waterdissolve in water

With increasing temperature of the water With increasing temperature of the water however, less oxygen will remain however, less oxygen will remain dissolved in the waterdissolved in the water

Listed from strongest IMF to weakest IMF

IMFs

A solute:•Dissolves in water or other solvent•Changes phase if different from the solvent •Present in lesser amount

(if the same phase as the solvent)A solvent: •Retains its phase (if different from the solute)•Present in greater amount

(if the same phase as the solute)•Rule for predicting solubility:

Like dissolves Like

Naming carbon compoundsNaming carbon compoundsOrganic Chemistry Organic Chemistry NomenclatureNomenclature

Carbon with four valence electrons forms Carbon with four valence electrons forms four covalent bonds to achieve a stable four covalent bonds to achieve a stable octet (eight valence)octet (eight valence)

Organic chemistry is the branch of Organic chemistry is the branch of chemistry dealing with carbon chemistry dealing with carbon compounds.compounds.

Simple alkanes- Simple alkanes- carbon chains with single carbon chains with single bondsbonds

Methane- one carbonMethane- one carbon Ethane- two carbonsEthane- two carbons Propane- three carbonsPropane- three carbons Butane- four carbonsButane- four carbons Pentane- five carbonsPentane- five carbons Hexane- six carbonsHexane- six carbons Heptane- seven carbonsHeptane- seven carbons Octane- eight carbonsOctane- eight carbons

Memorize these.Memorize these.

HexaneHexane

Branching chains in alkanes

Same attractions (induced dipole-induced dipole attractions)

Different states of matter-

What difference explains this?

Alkenes- Alkenes- a double between two carbon a double between two carbon atomsatoms

Ethene (also known as acetylene)Ethene (also known as acetylene)

C = CC = C

Use the alkane name. Use the alkane name. Add a double bondAdd a double bond Adjust the number of hydrogensAdjust the number of hydrogens

H

H

H

H

Alkynes- Alkynes- a triple bond between a triple bond between

two carbon atomstwo carbon atoms Ethyne (also known as acetylene)Ethyne (also known as acetylene)

H C C HH C C H

Use the alkane name. Use the alkane name. Add a triple bondAdd a triple bond Adjust the number of hydrogensAdjust the number of hydrogens

ethene

ethyne

Acteylene torches are used in welding.

The combustion of ethyne.

Again, notice the Again, notice the difference in boiling difference in boiling pointspoints

AlcoholsAlcohols

Alcohol functional group -OHAlcohol functional group -OH Add the alcohol functional group to an Add the alcohol functional group to an

alkane or other hydrocarbonalkane or other hydrocarbon Add the –ol ending to the nameAdd the –ol ending to the name ExampleExample

Methanol Methanol EthanolEthanol

Methanol

methanol

methanol

Alcohol- part polar and Alcohol- part polar and part nonpolarpart nonpolar

Antifreeze- soluble in water due to the polar part

Note: two alcohol groups attached

Organic AcidsOrganic Acids

Carboxyl group - COOHCarboxyl group - COOH The hydrogen sometimes breaks off the The hydrogen sometimes breaks off the

carboxyl group making this an acid in carboxyl group making this an acid in solutionsolution

Add the carboxyl groupAdd the carboxyl group Adjust the number of hydrogens Adjust the number of hydrogens

accordinglyaccordingly Add –oic acid to alkane nameAdd –oic acid to alkane name

Ethanoic AcidAlso known as acetic acid or

vinegar

Ethan- therefore 2 carbons-oic acid add –COOH

Polarity and AlkanesPolarity and Alkanes

C-H bond C-H bond EN of carbon 2.5EN of carbon 2.5 EN of hydrogen 2.1EN of hydrogen 2.1 Therefore the bond is nonpolarTherefore the bond is nonpolar

Alkanes are nonpolarAlkanes are nonpolar Alkanes will NOT dissolve in waterAlkanes will NOT dissolve in water

Polarity and AlcoholPolarity and Alcohol

C-H bond is nonpolarC-H bond is nonpolar O-HO-H

EN of oxygen 3.5EN of oxygen 3.5 EN of hydrogen 2.1EN of hydrogen 2.1 Difference in EN is 1.4Difference in EN is 1.4 Therefore the bond is polarTherefore the bond is polar

Alcohol molecules are polarAlcohol molecules are polar Alcohol molecules will dissolve in waterAlcohol molecules will dissolve in water

The longer the nonpolar The longer the nonpolar hydrocarbon chain the less hydrocarbon chain the less soluble the alcoholsoluble the alcohol

more soluble in water less soluble in water

Attractions and Size Attractions and Size determine the state of determine the state of compoundcompound

Differences in AttractionsDifferences in Attractions Compare ethane and ethanolCompare ethane and ethanol

Ethane is nonpolar, so attractions between Ethane is nonpolar, so attractions between the molecules are weak induced dipole-the molecules are weak induced dipole-induced dipole attractions.induced dipole attractions.

Ethanol is polar, so the attractions between Ethanol is polar, so the attractions between the molecules are dipole-dipole attractionsthe molecules are dipole-dipole attractions

With weaker attractions between the With weaker attractions between the molecules ethane is a gas at room molecules ethane is a gas at room temperature, while ethanol is a liquid temperature, while ethanol is a liquid

Given the same attractions between molecules, size can be used as a predictor of state

Differences in Size

Attractions and Vapor Attractions and Vapor PressurePressure

Ethane will have a higher vapor pressure Ethane will have a higher vapor pressure than ethanol at the same temperaturethan ethanol at the same temperature

With weaker attractions between the With weaker attractions between the molecules, more molecules will escape molecules, more molecules will escape the liquid and move into the gas phase the liquid and move into the gas phase causing more collisions and a greater VPcausing more collisions and a greater VP

With a higher VP a lower temperature is With a higher VP a lower temperature is required to get the liquid to boilrequired to get the liquid to boil

Which liquid has a higher boiling point?

What is the boiling point of each liquid at standard pressure?

Normal pressure (1 atm or 760 mm Hg

Boiling and Boiling and Vapor PressureVapor Pressure

Boiling occurs when the vapor pressure Boiling occurs when the vapor pressure (collisions of the molecules that have (collisions of the molecules that have escaped the liquid) equals the external or escaped the liquid) equals the external or outside pressureoutside pressure

On the previous graphOn the previous graph Find the “normal” boiling point of ethanol and Find the “normal” boiling point of ethanol and

heptaneheptane Find the boiling point of three liquids at 500 Find the boiling point of three liquids at 500

mm Hgmm Hg

Which liquid has greater attractions between the molecules?

If the outside pressure is 200 mmHg what is the BP temp?

If the outside pressure is 400 mmHg and the temperature is 10C, will CS2 be a liquid or gas?

Notice the difference in the axis- pressure compared temperature

This is external pressure to show the state given different combinations of pressure and temperature

S ℓ

ℓ g

S g

Critical point

triple point

Lab 2.2Lab 2.2

Adding Different Solids to WaterAdding Different Solids to Water

ConductivityConductivity

Electrical current is a flow of chargeElectrical current is a flow of charge Conductivity indicatorConductivity indicator

Light glows if substance conducts Light glows if substance conducts to complete circuitto complete circuit

In order to conduct electricity:In order to conduct electricity: Must have charged particlesMust have charged particles Must be able moveMust be able move

Conductivity of SolidsConductivity of Solids

Solids that conductSolids that conduct Metal elementsMetal elements Composed of atomsComposed of atoms

Atoms held in fixed Atoms held in fixed positions by metallic bondspositions by metallic bonds

Metallic bondMetallic bond Sea of free moving Sea of free moving

electrons shared by all the electrons shared by all the atomsatoms

Charged particles (e-) are Charged particles (e-) are free to movefree to move

Solids that do NOT conductSolids that do NOT conduct Nonmetal elementsNonmetal elements Composed of moleculesComposed of molecules Molecules are held Molecules are held

together by covalent together by covalent bonds between the atoms bonds between the atoms within the moleculeswithin the molecules

Molecules have no Molecules have no charge and cannot move, charge and cannot move, so do not conductso do not conduct

Ionic SolidsIonic Solids

While the ions have a chargeWhile the ions have a charge They are not free to move in the solidThey are not free to move in the solid The solid does NOT conduct electricityThe solid does NOT conduct electricity

- +

-+

--+

+

IONIC BONDS

hold the ions in fixed positions

Ionic Crystal LatticeIonic Crystal Lattice

The ionic compound has different The ionic compound has different properties than its elements.properties than its elements.

Conductivity of SolutionsConductivity of Solutions

Solutions that conductSolutions that conduct Ionic compoundsIonic compounds Combination of Combination of

Metals and NonmetalsMetals and Nonmetals

Composed of ionsComposed of ions Ions are free to move Ions are free to move

in solution, so the in solution, so the solution conducts solution conducts electricityelectricity

Solutions that do NOT Solutions that do NOT conductconduct

Covalent CompoundsCovalent Compounds Combination of Combination of

Nonmetals and NonmetalsNonmetals and Nonmetals

Composed of Composed of moleculesmolecules

Molecules are free to Molecules are free to move, but have no move, but have no chargecharge

Electrolytes conduct Electrolytes conduct electricity in solution.electricity in solution.

•Strong electrolytes: •Conduct current very efficiently. •completely ionized when they are dissolved in water •(soluble salts, strong acids, strong bases).•Weak electrolytes: •Conduct only a small current. •exhibit a small degree of ionization in water •(weak acids, weak bases).•Non electrolytes: •Permit no current to flow. •that dissolve in water but do not produce any ions. •(pure water, sugar solution).

AcidAcid is a substance that produces H is a substance that produces H++ ion (protons) when dissolve in water. ion (protons) when dissolve in water. HCl, HHCl, H22SOSO44

BaseBase is a substance that produces OH is a substance that produces OH-- ion (hydroxide) when dissolve in water. ion (hydroxide) when dissolve in water. NaOHNaOH

Ionic Compounds Ionic Compounds dissociate in solutiondissociate in solution

Ions split up Ions split up DissociateDissociate Ionic bonds break between ionsIonic bonds break between ions

Separated ions are attracted to water Separated ions are attracted to water moleculesmolecules Ion-dipole attractions form between ions and Ion-dipole attractions form between ions and

water moleculeswater molecules Ions are surrounded by water moleculesIons are surrounded by water molecules

Ions dissociate in solution.

Ions are attracted to the oppositely charged ends of water molecules by ion-dipole attractions

dipole

ion

Water- a dipole

With two oppositely charged ends

Ions attracted to oppositely-charged ends of water molecule

ION-DIPOLE ATTRACTION

Energy Change Energy Change Associated with DissolvingAssociated with Dissolving

Ionic bond break

Ion-dipole attractions form

Net change +2 kJ/molNote: the net change in energy +9 kJ/mol

Energy absorbed to break ionic bonds

Energy released as

ion-dipole attractions form

Calcium chloride dissolves in water Calcium chloride dissolves in water

The temperature of the solution increasesThe temperature of the solution increases Describe the direction of energy transfer.Describe the direction of energy transfer.

Energy must be transferred out of the system to the surroundings Energy must be transferred out of the system to the surroundings increasing the kinetic energy (must have been PE before the reaction)increasing the kinetic energy (must have been PE before the reaction)

Is the reaction endothermic or exothermic?Is the reaction endothermic or exothermic? An exothermic reactionAn exothermic reaction

What bonds must be broken?What bonds must be broken? Energy must be transferred in to break ionic bondsEnergy must be transferred in to break ionic bonds

What attractions are formed?What attractions are formed? Energy is transferred out as the ion-dipole attractions breakEnergy is transferred out as the ion-dipole attractions break

Is more energy transferred in or out? Is more energy transferred in or out? Since the net energy change is negative, more energy was Since the net energy change is negative, more energy was

transferred out than in for an overall net transfer outtransferred out than in for an overall net transfer out

Calcium chloride Calcium chloride dissolves in waterdissolves in water

Energy in to break ionic bonds

Energy out as ion-dipole attractions form

Net change in enthalpy

Enthalpy

CaCl2(s)

Ca2+(aq) + 2Cl- (aq)

Ionic solid with ionic bonds between the ions

Water with dipole-dipole attractions between the water molecules

Ionic bonds break

Ions dissociate

Ions move between water molecules

Ion-dipole attractions form

Solution conducts electricity since charged particles (the ions) are free to move

Visualize the solution with ions and water molecules in motion

Ammonium nitrate dissolves in Ammonium nitrate dissolves in waterwater

The temperature of the solution decreasesThe temperature of the solution decreases Describe the direction of energy transfer.Describe the direction of energy transfer.

Energy must be transferred into the system from the Energy must be transferred into the system from the surroundings, since the temperature of the surroundings surroundings, since the temperature of the surroundings decreases that KE must have been transferred into the systemdecreases that KE must have been transferred into the system

Is the reaction endothermic or exothermic?Is the reaction endothermic or exothermic? An endothermic reactionAn endothermic reaction

What bonds must be broken?What bonds must be broken? Energy must be transferred in to break ionic bondsEnergy must be transferred in to break ionic bonds

What attractions are formed?What attractions are formed? Energy is transferred out as the ion-dipole attractions breakEnergy is transferred out as the ion-dipole attractions break

Is more energy transferred in or out? Is more energy transferred in or out? Since the net energy change is positive, more energy was Since the net energy change is positive, more energy was

transferred in than out for an overall net transfer intransferred in than out for an overall net transfer in

Ammonium nitrate Ammonium nitrate dissolves in waterdissolves in water

Energy in to break ionic bonds

Energy out as ion-dipole attractions form

Net change in enthalpy

Enthalpy

NH4NO3(s)

NH4+(aq) + NO3

- (aq)

Electrical Force and ion-dipole Electrical Force and ion-dipole AttractionsAttractions

Ion-dipole attraction is the attraction Ion-dipole attraction is the attraction between charges therefore an electrical between charges therefore an electrical forceforce

Electrical force depends upon bothElectrical force depends upon both Charge Charge

(increase charge – increase force)(increase charge – increase force)

Distance Distance (decrease distance- increase force)(decrease distance- increase force)

With a greater positive charge, the Mg2+ ion is more attracted to the water molecule than Li+1. Remember: electrical force depends on magnitude of charge- greater charge greater electrical force

With a greater size, the K+1 ion cannot get as close to the water molecule as the smaller Li+1ion. With a lesser distance, the electrical force is greater Remember: electrical force depends on distance- greater distance lesser electrical force

Inorganic Nomenclature- Inorganic Nomenclature- Covalent compoundsCovalent compounds

Covalent – Covalent – Nonmetal/Nonmetal CombinationsNonmetal/Nonmetal Combinations Use prefixes to indicate number of atomsUse prefixes to indicate number of atoms

Mono (1)Mono (1) Di (2)Di (2) Tri (3)Tri (3) Tetra (4)Tetra (4)

Example Example Carbon dioxide (COCarbon dioxide (CO22)) Carbon tetrachloride (CClCarbon tetrachloride (CCl44)) Disulfur trioxide (SDisulfur trioxide (S22OO33))

IonicIonic - Metal/Nonmetal Combinations - Metal/Nonmetal Combinations

Inorganic Nomenclature- Inorganic Nomenclature- Ionic compoundsIonic compounds

IonicIonic - Metal/Nonmetal Combinations - Metal/Nonmetal Combinations Use charges on the ions to find ratio of ions in neutral compoundUse charges on the ions to find ratio of ions in neutral compound Metal listed first, nonmetal listed second with ending changed to –ideMetal listed first, nonmetal listed second with ending changed to –ide ExampleExample

Calcium (+2) chloride (-1) CaClCalcium (+2) chloride (-1) CaCl22

Sodium (+1) sulfide (-2) NaSodium (+1) sulfide (-2) Na22SS Transition metals- form ions with different chargesTransition metals- form ions with different charges

Iron (III) FeIron (III) Fe3+3+ and Iron (II) Fe and Iron (II) Fe2+2+ Copper (II) CuCopper (II) Cu2+2+ and Copper (I) Cu and Copper (I) Cu++

Polyatomic ionsPolyatomic ions Nitrate Nitrate (NO(NO33

--)) Carbonate (COCarbonate (CO33

2-2-)) Sulfate (SOSulfate (SO44

2-2-)) Ammonium (NHAmmonium (NH44

++)) Hydroxide (OH-)Hydroxide (OH-)

Inorganic NomenclatureInorganic Nomenclature

Acids Acids Positive hydrogen ionsPositive hydrogen ions And a negative ionWith monoatomic ionsAnd a negative ionWith monoatomic ions

Hydro—ic acidHydro—ic acid Ex. Hydrochloric acid H w/ ClEx. Hydrochloric acid H w/ Cl Ex. Hydrobromic acid H w/ BrEx. Hydrobromic acid H w/ Br Ex. Hydrosulfuric acid H w/ SEx. Hydrosulfuric acid H w/ S

With polyatomic –ate ionsWith polyatomic –ate ions ——ic acidic acid Ex. Sulfuric acid H with sulfate (HEx. Sulfuric acid H with sulfate (H22SOSO44)) Ex. Nitric acid H with nitrate (HNOEx. Nitric acid H with nitrate (HNO33))

With polyatomic –ite ionsWith polyatomic –ite ions ——ous acidous acid Ex. Sulfurous acid H with sulfite(HEx. Sulfurous acid H with sulfite(H22SOSO33)) Ex. Nitrous acid H with nitrite(HNOEx. Nitrous acid H with nitrite(HNO22))

Polyatomic IonsPolyatomic Ions

Polyatomic ions are charged groups of covalently bonded atoms

Formulas and Names Formulas and Names for Acidsfor Acids

EOS

Ternary acids simply use the polyatomic anion name with “ate” changing to “ic” plus the word acid

Oxidation NumbersOxidation Numbers

Assigned values that allow us to track the Assigned values that allow us to track the electronselectrons

Represent a relative share of electronsRepresent a relative share of electrons Oxidation allow us to identify the species Oxidation allow us to identify the species

oxidized and reducedoxidized and reduced

Rules for assigning Oxidation Rules for assigning Oxidation Numbers #1Numbers #1

elements and monoatomic ionselements and monoatomic ions Uncombined elements have oxidation Uncombined elements have oxidation

numbers of zero numbers of zero

ex. Oxygen Oex. Oxygen O22 oxid # is 0 oxid # is 0

ex. Iron Fe oxid # is 0ex. Iron Fe oxid # is 0 Monoatomic ions have oxid # is the Monoatomic ions have oxid # is the

charge on the ioncharge on the ionex. Iron (III) ion Feex. Iron (III) ion Fe3+3+ oxid # is +3 oxid # is +3ex. Chloride ion Clex. Chloride ion Cl-- oxid # is -1 oxid # is -1

Rules for assigning Oxidation Rules for assigning Oxidation Numbers #2Numbers #2

Hydrogen and OxygenHydrogen and Oxygen Hydrogen oxid # is usually +1Hydrogen oxid # is usually +1

Unless Unless

as uncombined element Has uncombined element H2 2 then 0then 0or in metal hydride then -1or in metal hydride then -1

Oxygen oxid # is usually -2Oxygen oxid # is usually -2Unless Unless

as uncombined element Oas uncombined element O2 2 then 0then 0or in peroxide ion then -1or in peroxide ion then -1

Rules for assigning Oxidation Rules for assigning Oxidation Numbers #3Numbers #3

Calculating Other Oxidation numbersCalculating Other Oxidation numbers

Sum of oxidation numbers for neutral compounds will Sum of oxidation numbers for neutral compounds will be zerobe zero Ex. SOEx. SO22 Since the oxygen must be -2 and there are two of Since the oxygen must be -2 and there are two of

them, the sulfur must be +4 so that the sum will be zerothem, the sulfur must be +4 so that the sum will be zero Ex. NHEx. NH33 Since the hydrogen must be +1 and there are three of Since the hydrogen must be +1 and there are three of

them, the nitrogen must be -3 so that the sum will be zerothem, the nitrogen must be -3 so that the sum will be zero Sum of oxidation numbers for polyatomic ions will be Sum of oxidation numbers for polyatomic ions will be

the charge on the ionthe charge on the ion Ex. NOEx. NO33

-- Since the oxygen must be -2 and there are three of Since the oxygen must be -2 and there are three of them, the nitrogen must be +5 so that the sum will be -1them, the nitrogen must be +5 so that the sum will be -1

Ex. NHEx. NH44++ Since the hydrogen must be +1 and there are four of Since the hydrogen must be +1 and there are four of

them, the nitrogen must be -3 so that the sum will be +1them, the nitrogen must be -3 so that the sum will be +1