CHEMICAL CHEMICAL EQUATIONSEQUATIONS

11

Water and what is known from its Water and what is known from its equation.equation.

2H2H22 ++ OO22 →→ 2H2H22OO

hydrogenhydrogen ++ oxygenoxygen →→ waterwater

4 atoms H4 atoms H ++ 2 atoms O2 atoms O →→ 4 atoms H + 4 atoms H +

2 atoms O2 atoms O

2 molecules H + 1 molecule O → 2 molecules water

2 moles H 2 moles H ++ 1 mole O1 mole O →→ 2 moles water *** 2 moles water ***

4 amu H 4 amu H ++ 32 amu O 32 amu O →→ 36 amu water 36 amu water

4 grams H 4 grams H ++ 32 grams O32 grams O →→ 36 grams water 36 grams water

*** Note that molecules and moles always have the SAME RATIOS 22

CHEMICAL REACTIONSCHEMICAL REACTIONS

one or more substances are changed one or more substances are changed into different substancesinto different substances

Represented by chemical equationsRepresented by chemical equations• 2H2H22 (g) + O (g) + O22(g) (g) 2H 2H22O(g)O(g)

REACTANTSREACTANTS PRODUCTS PRODUCTS

33

Show the substances undergoing Show the substances undergoing change and the result(s).change and the result(s).

Show relative amts. of Show relative amts. of elements/cmpds. that take part in elements/cmpds. that take part in the changes the changes [coefficients][coefficients]

See ‘Symbols Used in Chem. Rxn. See ‘Symbols Used in Chem. Rxn. handouthandout

CHEMICAL EQUATIONSCHEMICAL EQUATIONS

44

Writing Chemical EquationsWriting Chemical Equations11.1

55

66

Writing Chemical EquationsWriting Chemical Equations

iron + oxygen iron + oxygen iron(III) oxide iron(III) oxide

11.1

77

Writing Chemical EquationsWriting Chemical Equations

Hydrogen Peroxide Hydrogen Peroxide Water and Oxygen Water and Oxygen

11.1

88

The PVC Method The PVC Method to to WRITING A BALANCED CHEMICAL EQUATIONWRITING A BALANCED CHEMICAL EQUATION

99

•Pair the elements properly

•Valences give subscripts

•Coefficients balance the equation

WRITING A BALANCED WRITING A BALANCED CHEMICAL EQUATIONCHEMICAL EQUATION

Tips:Tips:

Start with element that appears only once Start with element that appears only once on each side.on each side.

Save oxygen and hydrogen for lastSave oxygen and hydrogen for last

1010

Lithium aluminum hydrideLithium aluminum hydride reacts with reacts with waterwater to to produce produce lithium hydroxidelithium hydroxide, , aluminum aluminum

hydroxidehydroxide and and hydrogen gashydrogen gas..

LiAlHLiAlH4 4 + H+ H22O O LiOH + Al(OH) LiOH + Al(OH)33 + H + H22

LiAlHLiAlH44 + + 44HH22O O LiOH + Al(OH) LiOH + Al(OH)33 + +

HH22

LiAlHLiAlH44 + + 44HH22O O LiOH + Al(OH) LiOH + Al(OH)33 + +

44HH22

*Note that hydrogen is *Note that hydrogen is didiatomic when not atomic when not bonded to other elements.bonded to other elements. 1111

Diatomic MoleculesDiatomic Molecules

HHarvey arvey BrOFINClBrOFINCl

H. BrOFINCl

1212

Persistent difficulty ?Persistent difficulty ?

Check all FORMULAS to make sure they are correctCheck all FORMULAS to make sure they are correct

• KK22(SO(SO44) v K) v K22(SO(SO33))

1313

Ammonia reacts with oxygen gas to Ammonia reacts with oxygen gas to produce nitrogen dioxide and produce nitrogen dioxide and

water.water.

NHNH33 + O + O22 NO NO22 + H + H22OO 22NHNH33 + O + O22 NO NO2 2 + + 33HH22OO 22NHNH33 + O + O22 22NONO2 2 + + 33HH22OO 22NHNH33 + + 7/27/2OO22 22NONO2 2 + + 33HH22OO 44NHNH33 + + 77OO22 44NONO22 + + 66HH22OO

1414

SynthesisSynthesis

1515

Common Types of Chemical Common Types of Chemical ReactionsReactionsSynthesisSynthesis

two or more simple compounds two or more simple compounds combine to form a more complicated combine to form a more complicated one one

General form : General form : A + B ---> ABA + B ---> AB

Iron and sulfur to form iron (II) Iron and sulfur to form iron (II) sulfide:sulfide:

8 Fe + S8 Fe + S88 ---> 8 FeS ---> 8 FeS

1616

DecompositionDecomposition

1717

Common Types of Chemical Common Types of Chemical ReactionsReactions

DecompositionDecomposition opposite of a synthesis reaction opposite of a synthesis reaction complex molecule breaks down to complex molecule breaks down to

make simpler ones make simpler ones General form: General form: AB ---> A + BAB ---> A + B

Hydrogen peroxide decomposes to water and Hydrogen peroxide decomposes to water and oxygen gas:oxygen gas:

HH22OO22 H H22O +OO +O22

1818

Single ReplacementSingle Replacement

1919

Common Types of Chemical Common Types of Chemical ReactionsReactions

Single ReplacementSingle Replacement one element trades places with one element trades places with

another element in a compound another element in a compound General form: General form: AA+++ BC ---> AC + B+ BC ---> AC + B, ,

or or AA-- + BC ---> BA + C + BC ---> BA + C

Zinc replaces copper in copper sulfide solution:Zinc replaces copper in copper sulfide solution:

Zn +Zn + CuSOCuSO4 4 ZnSO ZnSO4 4 + Cu+ Cu

2020

Double ReplacementDouble Replacement

2121

Common Types of Chemical Common Types of Chemical ReactionsReactions

Double ReplacementDouble Replacement cations (positive ions) of two different cations (positive ions) of two different

molecules switch places, forming two molecules switch places, forming two entirely different compounds entirely different compounds

General form: General form:

AB + CD ---> AD + CBAB + CD ---> AD + CB Sodium Chloride (salt) solution reacts with silver Sodium Chloride (salt) solution reacts with silver

nitrate to produce silver chloride and sodium nitrate to produce silver chloride and sodium nitrate.nitrate.

NaCl +AgNONaCl +AgNO3 3 AgCl AgCl + NaNO + NaNO332222

2323

Common Types of Chemical Common Types of Chemical ReactionsReactions

CombustionCombustion oxygen combines with a compound oxygen combines with a compound

containing carbon, hydrogen and containing carbon, hydrogen and sometimes oxygen sometimes oxygen

forms forms waterwater and and carbon dioxidecarbon dioxide. . General Form: General Form: CCxxHHyy CO CO22 + H + H22OO Exothermic Exothermic Burning of naphthalene: Burning of naphthalene:

CC1010HH88 + 12 O + 12 O22 ---> 10 CO ---> 10 CO22 + 4 H + 4 H22OO2424

Review and ForeshadowReview and Foreshadow

Video• Logic and rules for balancing chemical Logic and rules for balancing chemical

equations are reviewedequations are reviewed• Types of chemical reactions are introducedTypes of chemical reactions are introduced

Take NotesTake Notes Quiz (10 points) @ end of videoQuiz (10 points) @ end of video

• NameName• PeriodPeriod• Number 1-10Number 1-10

2525

Decomposition: Special Decomposition: Special CasesCases

Anions and cations do not separate Anions and cations do not separate as expected.as expected.

X = any metalX = any metal

2626

Metal carbonates Metal carbonates

XCOXCO3 3 XO + CO XO + CO22 metal oxide & carbon dioxidemetal oxide & carbon dioxide

CaCOCaCO33 CaO + CO CaO + CO22

2727

Metal hydroxidesMetal hydroxides

XOH XOH XO + H XO + H22O O metal oxide & watermetal oxide & water

Ca(OH)Ca(OH)22 CaO + H CaO + H22OO

2828

Metal chloratesMetal chlorates

XClOXClO33 XCl + O XCl + O22 metal chloride & oxygen gasmetal chloride & oxygen gas

Ca(ClOCa(ClO33))22 CaCl CaCl22 + 3O + 3O22

2929

Single Replacement Single Replacement ReactionsReactions

AA+++ BC ---> AC + B, or+ BC ---> AC + B, or AA- - + BC ---> BA + C + BC ---> BA + C

Are the free elements always able to Are the free elements always able to replace the element in the compound?replace the element in the compound?

How can we tell when / if the free How can we tell when / if the free elements will successfully replace the elements will successfully replace the element in the compound?element in the compound?

3030

Activity Series [partial listing]Activity Series [partial listing]

MetalsMetals Decreasing Decreasing ActivityActivity

HalogensHalogens

lithium lithium ↓↓ fluorinefluorine

potassiumpotassium ↓↓ chlorine chlorine

calcium calcium ↓↓ bromine bromine

sodium sodium ↓↓ oxygenoxygen

magnesiummagnesium ↓↓ iodine iodine

aluminumaluminum ↓↓ sulfur sulfur

zinc zinc ↓↓

chromium chromium ↓↓

ironiron ↓↓ 3131

Will these reactions occur?Will these reactions occur?

ZnCOZnCO33 + H + H22 ?? ZnCOZnCO33 + H + H22 N.R.N.R.

AgCl + Mg AgCl + Mg ?? 2AgCl + Mg 2AgCl + Mg MgClMgCl22 + 2Ag + 2Ag

3232

Replacing HYDROGEN in WATERReplacing HYDROGEN in WATER

Water is Water is unusually stableunusually stable..

Replacing the hydrogen in water depends Replacing the hydrogen in water depends on:on:• Placement of free element on Placement of free element on activity activity

series, series, andand• TEMPERATURETEMPERATURE

3333

Replacing HYDROGEN in WATERReplacing HYDROGEN in WATER

• << 175 oC 175 oC X + HX + H22O O X XOHOH + H + H22

Metal hydroxide hydrogen gasMetal hydroxide hydrogen gas Ca + 2HCa + 2H22O O Ca(OH) Ca(OH)22 + H + H22

• > 175oC> 175oC X + HX + H22O O X XOO + H + H22

Metal oxide hydrogen gasMetal oxide hydrogen gas Ca + HCa + H22O O CaO + H CaO + H22

3434

Double Replacement Double Replacement ReactionsReactions

AB + CD ---> AD + CBAB + CD ---> AD + CB When a double replacement When a double replacement

reaction occurs one of the reaction occurs one of the following are produced:following are produced:• gasgas• precipitateprecipitate

an insoluble solid that forms when two an insoluble solid that forms when two liquids are mixedliquids are mixed

• waterwater These rxn also called acid-base rxnThese rxn also called acid-base rxn

3535

SOLUBILITYSOLUBILITY The property of a substance to dissolveThe property of a substance to dissolve

• WaterWater• Universal solventUniversal solvent

Solubility Table - handoutSolubility Table - handout

NaCl + AgNONaCl + AgNO33 NaNO NaNO33 + AgCl + AgCl 2NaCl + Fe(NO2NaCl + Fe(NO33))22 2NaNO 2NaNO33 + FeCl + FeCl2 2 NR NR (no double replacement(no double replacement

products made)products made)

3636

Predicting Reaction ProductsPredicting Reaction Products

Analyze the reactants. Analyze the reactants. Decide what Decide what patternpattern of chemical of chemical

reaction the reactants will fit.reaction the reactants will fit.

Na and HNa and H22SOSO44

• a a single elementsingle element and a and a compoundcompound fit the fit the

single replacementsingle replacement pattern. pattern. HH22 and O and O22

• two elements fit the two elements fit the synthesissynthesis pattern pattern..

3737

Use the pattern to decide which Use the pattern to decide which elements will go together. elements will go together.

[REMEMBER to refer to the [REMEMBER to refer to the Activity SeriesActivity Series for for single replacement reactions.]single replacement reactions.]

Na + HNa + H22SOSO44 → →

• Na replaces H [Na stronger than H]; H Na replaces H [Na stronger than H]; H becomes lone element.becomes lone element.

• 2Na + H2Na + H22SOSO44 → Na → Na22SOSO4 4 + H + H22

3838

Use Use valences valences to form good chemical to form good chemical formulas to represent the products. formulas to represent the products.

The sum of the valences equals The sum of the valences equals zerozero in a in a chemical formula.chemical formula.

NaNa+1+1; SO; SO44--22

• 2Na + H2Na + H22SOSO44 → Na → Na22SOSO44 + H + H22

Write the diatomic elements as HWrite the diatomic elements as H22, Br, Br22, O, O22, , FF22, I, I22, N, N22, and Cl, and Cl22. when they are . when they are by by themselves.themselves.. (H. (Henry enry BrOFINCl)BrOFINCl)

• 22HH22 + + OO22 → 2H → 2H22O O 3939

Balance the equations using Balance the equations using coefficientscoefficients

(BIG numbers placed in FRONT of the chemical formula.)(BIG numbers placed in FRONT of the chemical formula.)

22Na + HNa + H22SOSO44 → Na → Na22SOSO44 + H + H22 22HH22 + O + O22 → → 22HH22O O

Balance Balance H, OH, O lastlast..

4040

Nuclear EquationsNuclear Equations

Nuclear equations result in the Nuclear equations result in the change of one element into another change of one element into another

transmutationtransmutation • 238238 number of protons + neutrons number of protons + neutrons

92 92 UU number of protons number of protons (determines identity of (determines identity of atom)atom)

4141

4242

α particle decayα particle decay

238238 234 4 234 4

9292 U U 9090 Th + Th + 22HeHe thorium α particlethorium α particle

4343

β particle decayβ particle decay 234 234 0234 234 0

9090 Th Th 9191 Pa + - Pa + -11e-e- protactinium β particleprotactinium β particle

Decay continues until a stable Decay continues until a stable substance is reached.substance is reached.

4444

K capture decayK capture decay 100 0 100100 0 100

4646 Pd + - Pd + -11e- e- 4545 Rh Rh

4545

Rules for balancing nuclear Rules for balancing nuclear equationsequations

The sum of the mass numbers (top) The sum of the mass numbers (top) is the same on both sides of the is the same on both sides of the equation.equation.

The sum of the electric charges The sum of the electric charges (bottom) is the same on both sides of (bottom) is the same on both sides of the equation.the equation.

4646

Find the unknown productFind the unknown product

18 018 0 9F 9F +1 e- + ? +1 e- + ?

Find the massFind the mass 18 = 0 + x18 = 0 + x 18 = x18 = x

18 0 18 0 1818 9 F 9 F + 1e- + ? + 1e- + ?

4747

230?V X230?V X

Find the chargeFind the charge

9 = 1 + x9 = 1 + x 8 = x8 = x

18 0 1818 0 18

9F 9F +1e- + +1e- + 88 ? ?

4848

Find the element Find the element

18 0 1818 0 18

99F F +1+1e- + e- + 88 OO

4949