chemical equations unit 3 module 1

Chemical EquationsChemical Equations

Unit 3 Module 1Unit 3 Module 1

Counting Atoms ReviewCounting Atoms ReviewCo-efficientCo-efficient

The large number in front of a The large number in front of a compound representing the number of compound representing the number of units taking part in the reactionunits taking part in the reaction

SubscriptSubscriptTells how many atoms are in each Tells how many atoms are in each

moleculemolecule

Subscripts counted for that element onlySubscripts counted for that element onlyHH22O = 2 ATOMS of HYDROGENO = 2 ATOMS of HYDROGEN

Counting Atoms ReviewCounting Atoms ReviewCoefficients counted for every element in Coefficients counted for every element in

the compoundthe compound2 H2 H22OO

H = 4H = 4O = 2O = 2

4Al4Al22(SO(SO44))33

Aluminum: 2 * 4 = 8Aluminum: 2 * 4 = 8Sulfur: 1*3 = 3 * 4 = 12Sulfur: 1*3 = 3 * 4 = 12Oxygen: 4 * 3 = 12 * 4 = 48Oxygen: 4 * 3 = 12 * 4 = 48

Chemical ReactionsChemical ReactionsWhen bonds are broken and new bonds When bonds are broken and new bonds

are formedare formed

Energy is released from the old bonds Energy is released from the old bonds and stored in the new bondsand stored in the new bonds

New combination of elementsNew combination of elements

Chemical properties in new substances Chemical properties in new substances are different from the properties of the are different from the properties of the old substancesold substances

Evidence of Chemical ReactionsEvidence of Chemical Reactions

A gas is formed (Bubbles)A gas is formed (Bubbles)

A Precipitate is formed (Turns cloudy because a A Precipitate is formed (Turns cloudy because a new solid forms)new solid forms)

There is a energy / temperature change There is a energy / temperature change (Because bonds are breaking and re-forming)(Because bonds are breaking and re-forming)

There is a color change (Because new There is a color change (Because new substances are formingsubstances are forming

Light is producedLight is produced

Chemical EquationsChemical EquationsAn expression that describes a chemical An expression that describes a chemical

reactionreaction

2Mg + O2Mg + O22 2MgO2MgO

Chemical Equation LanguageChemical Equation Language REACTANTSREACTANTS PRODUCTSPRODUCTS

2Mg + O2Mg + O22 2MgO2MgO

ReactantsReactantsOn the left of the arrowOn the left of the arrowThe elements/compounds you start withThe elements/compounds you start with2Mg + O2Mg + O22

ProductsProductsOn the right of the arrowOn the right of the arrowThe elements/ compounds you finish withThe elements/ compounds you finish with2MgO2MgO

Chemical Equation LanguageChemical Equation Language

REACTANTSREACTANTS PRODUCTSPRODUCTS

ArrowArrow““Yields” or “Results in”Yields” or “Results in”Separates the reactants from the productsSeparates the reactants from the products

Chemical Equation LanguageChemical Equation Language

3Fe3Fe(s)(s) + 4H + 4H22OO(l)(l) 1Fe1Fe33OO4(aq)4(aq) + 4H + 4H2(g)2(g)

(s)(s)This Reactant is in SOLID formThis Reactant is in SOLID form

(l)(l)This Reactant is in LIQUID formThis Reactant is in LIQUID form

(aq)(aq)This Product is in AQUEOUS form (Mixed with Water)This Product is in AQUEOUS form (Mixed with Water)

(g)(g)This Product is in GAS formThis Product is in GAS form

Practice: Counting AtomsPractice: Counting Atoms Fe(SOFe(SO44))

Fe = Fe = S = S = O = O =

4Cu(SO4Cu(SO44)) Cu = Cu = S = S = O = O =

6Zn(NO6Zn(NO33))22

Zn = Zn = N = N = O = O =

Practice: EquationsPractice: EquationsZnBrZnBr22 + 2Ag(NO + 2Ag(NO33)) Zn(NOZn(NO33))22 + 2AgBr + 2AgBr

What are the reactants?What are the reactants?

What are the products?What are the products?

How many molecules are there of AgBr?How many molecules are there of AgBr?

How many atoms of Oxygen are there in How many atoms of Oxygen are there in Ag(NOAg(NO33)?)?

Law of Conservation of MassLaw of Conservation of Mass Mass (matter) can be neither created or Mass (matter) can be neither created or

destroyed destroyed It just changes from one form to anotherIt just changes from one form to another

Example: BURNED WOODExample: BURNED WOOD

500g Wood500g Wood 300g Ash + 200g 300g Ash + 200g SmokeSmoke Reactant: 500g WoodReactant: 500g Wood Product: 300g Ash + 200g SmokeProduct: 300g Ash + 200g Smoke

TOTAL MASS OF THE PRODUCTS OF A TOTAL MASS OF THE PRODUCTS OF A REACTION IS EQUAL TO THE TOTAL MASS OF REACTION IS EQUAL TO THE TOTAL MASS OF THE REACTANTS.THE REACTANTS.

Law of Conservation of MassLaw of Conservation of Mass

2KClO2KClO33 2KCl + 3O2KCl + 3O22

If 500 grams of KClOIf 500 grams of KClO33 decomposes decomposes (breakdowns) and produces 303 grams of (breakdowns) and produces 303 grams of KCl, how many grams of OKCl, how many grams of O22 are produced? are produced?

500 grams 303 grams + ?500 grams 303 grams + ?

500 grams 500 grams 303 grams + 197 303 grams + 197 gramsgrams


2KI + Pb(NO2KI + Pb(NO33))22 PbIPbI22 + K(NO + K(NO33))

If 700 grams of the product is produced, If 700 grams of the product is produced, how many grams of KI do you start with if how many grams of KI do you start with if you also have 520 grams of Pb(NOyou also have 520 grams of Pb(NO33))22??

520 grams + ? 520 grams + ? 700 700 gramsgrams

520 grams + 180 grams520 grams + 180 grams 700 grams 700 grams


2H2H22S + OS + O22 HH22O + SO + S

If you have 250 grams of water and 380 If you have 250 grams of water and 380 grams of sulfur, how many grams of grams of sulfur, how many grams of oxygen do you have if you start with 400 oxygen do you have if you start with 400 grams of Hgrams of H22S?S?

? + 400g ? + 400g 250g + 380g 250g + 380g

? + 400g? + 400g 630g 630g

230g + 400g230g + 400g 630g 630g

Balanced Chemical EquationsBalanced Chemical EquationsShows Chemical Reactions in a Shows Chemical Reactions in a

Conservation of Mass formConservation of Mass form

The total mass of the reactants MUST The total mass of the reactants MUST equal the total mass of the productsequal the total mass of the products

A BALANCED EQUATION has the same A BALANCED EQUATION has the same ELEMENTS & the same # OF ATOMS in ELEMENTS & the same # OF ATOMS in BOTH the reactants and productsBOTH the reactants and products

Balancing Chemical EquationsBalancing Chemical Equations

IN A CHEMICAL EQUATION, THE # & TYPE IN A CHEMICAL EQUATION, THE # & TYPE OF ATOMS ON BOTH SIDES MUST BE OF ATOMS ON BOTH SIDES MUST BE EQUAL!!EQUAL!!

THIS IS NOT BALANCED!!!!THIS IS NOT BALANCED!!!!

HH22 + O + O22 H H22OO

H = 2H = 2 H = 2H = 2

O = 2O = 2 O = 1O = 1

Balancing Chemical EquationsBalancing Chemical EquationsONLY CO-EFFICIENTS MAY BE CHANGED ONLY CO-EFFICIENTS MAY BE CHANGED

OR ADDED TO BALANCE AN EQUATION!!!OR ADDED TO BALANCE AN EQUATION!!!THE NUMBER BEFORE THE COMPOUNDTHE NUMBER BEFORE THE COMPOUND

SUBSCRIPTS MAY SUBSCRIPTS MAY NOTNOT BE CHANGED OR BE CHANGED OR ADDED!!!!!ADDED!!!!!

THE SMALL NUMBER AFTER THE COMPOUNDTHE SMALL NUMBER AFTER THE COMPOUND

22HH22 + O + O22 22HH22OOBALANCEDBALANCED

How to BalanceHow to Balance

Write the equation with boxes in front of each Write the equation with boxes in front of each compoundcompound

HH22 + O + O22 H H22OO

Count the # of atoms of each element in the Count the # of atoms of each element in the reactants and the productsreactants and the products

H = 2H = 2 H = 2H = 2

O = 2O = 2 O = 1O = 1

If any numbers are different, the equation is If any numbers are different, the equation is NOT balancedNOT balanced

How to BalanceHow to BalanceChange ONLY the coefficients to balance Change ONLY the coefficients to balance

the equationthe equation

HH2 2 + O+ O22 2 2 HH22OOH = 2H = 2 H = 2 4H = 2 4O = 2O = 2 O = 1 2O = 1 2

The equation is BALANCED when the The equation is BALANCED when the same number of atoms of each element same number of atoms of each element are on BOTH sides of the equationare on BOTH sides of the equation

2 2 HH2 2 + 1 O+ 1 O22 2 2 HH22OOH = 2 4H = 2 4 H = 4H = 4

O = 2 2O = 2 2 O = 2O = 2

LET’S PRACTICE!!!LET’S PRACTICE!!!__CH__CH44 +__ O +__ O2 2 ____COCO2 2 + __H+ __H22OO

__Al +__Br__Al +__Br2 __2 __AlBrAlBr33

LET’S PRACTICE!!!LET’S PRACTICE!!!11 CH CH44 + + 22 O O2 2 11COCO2 2 + + 22 H H22OO

22 Al + Al + 33 Br Br2 2 2 2 AlBrAlBr33

LET’S PRACTICE!!!LET’S PRACTICE!!!

_SrCl_SrCl22 +_KNO +_KNO33 __ __ Sr(NOSr(NO33))22+_KCl+_KCl

__KOH +__H__KOH +__H22SOSO44 __K __K22SOSO44 +__H +__H22OO


11 SrCl SrCl22 + +22 KNO KNO33 1 1 Sr(NOSr(NO33))22++22 KCl KCl

22 KOH + KOH +11 H H22SOSO44 11 K K22SOSO44 + +22 H H22OO


__H__H22O +__NO +__N22OO33 __HNO__HNO22

__Fe +__H__Fe +__H22OO __Fe__Fe33OO44 + __H + __H22


11 H H22O +O +11 N N22OO33 22 HNO HNO22

33 Fe + Fe + 44 H H22OO 11 Fe Fe33OO44 + + 44 H H22


__C__C1212HH2222OO1111 + __H + __H22O O __C + __H __C + __H22OO

__Na__Na22(SO(SO44) +__BaCl) +__BaCl22 __BaSO __BaSO44+__NaCl+__NaCl


1 1 CC1212HH2222OO1111 + + 11 H H22O O 12 12 C + C + 1212 H H22OO

11 Na Na22(SO(SO44) + ) + 11 BaCl BaCl22 11 BaSO BaSO44+ + 22 NaCl NaCl


__PbO__PbO22 __PbO + __O__PbO + __O22

__Cl__Cl2 2 +__KBr+__KBr __KCl +__Br__KCl +__Br22


22 PbO PbO22 22 PbO + PbO + 11 O O22

11 Cl Cl2 2 ++22 KBr KBr 22 KCl + KCl + 11 Br Br22


__NaCl + __H__NaCl + __H22(SO(SO44)) __Na__Na22SOSO44 +__HCl +__HCl


22 NaCl + NaCl + 11 H H22(SO(SO44)) 11 Na Na22SOSO44 + + 22 HCl HCl

Ratios & Chemical EquationsRatios & Chemical Equations

Ratios are written #:#:#Ratios are written #:#:#

Use the Co-efficients when writing ratiosUse the Co-efficients when writing ratios

2 H2 H22 + 1 O + 1 O22 2 H 2 H22OO

RATIO FOR THIS EQUATION = RATIO FOR THIS EQUATION =

2:1:22:1:2

QUESTION:QUESTION:

If I have 10 molecules of OIf I have 10 molecules of O22, how many , how many molecules of Hmolecules of H22O do I have?O do I have?

2 H2 H22 + 1 O + 1 O22 2 H 2 H22OO


2:1:22:1:2

ANSWER:ANSWER:

If I have 10 molecules of OIf I have 10 molecules of O22, how many , how many molecules of Hmolecules of H22O do I have?O do I have?

2 H2 H22 + 1 O + 1 O22 2 H2 H22OO


2 : 1 : 22 : 1 : 2

Oxygen Coefficient = 10/1 = 10 moleculesOxygen Coefficient = 10/1 = 10 molecules

Water Coefficient = 2*10 = 20 MoleculesWater Coefficient = 2*10 = 20 Molecules

QUESTION:QUESTION:

If I have 30 molecules of HIf I have 30 molecules of H22O, how many O, how many molecules of Omolecules of O22 do I have? do I have?

2 H2 H22 + 1 O + 1 O22 2 H 2 H22OO


2:1:22:1:2

ANSWER:ANSWER:

If I have 30 molecules of HIf I have 30 molecules of H22O, how many O, how many molecules of Omolecules of O22 do I have? do I have?

2 H2 H22 + 1 O + 1 O22 2 H 2 H22OO


2 : 1 : 22 : 1 : 2

Water = 30 molecules/2 = 15Water = 30 molecules/2 = 15

Oxygen = 1*15 = 15 MoleculesOxygen = 1*15 = 15 Molecules

QUESTION:QUESTION:

If I have 24 molecules of PbO, how many If I have 24 molecules of PbO, how many molecules of Pb do I have?molecules of Pb do I have?

PbS + 2 PbOPbS + 2 PbO 3 Pb + SO 3 Pb + SO22


__ : __ : __ : ____ : __ : __ : __

ANSWER:ANSWER:

If I have 24 molecules of PbO, how many If I have 24 molecules of PbO, how many molecules of Pb do I have?molecules of Pb do I have?

PbS + 2 PbOPbS + 2 PbO 3 Pb + SO 3 Pb + SO22


1 : 2 : 3 : 11 : 2 : 3 : 1

PbO = 24 molecules/2 = 12PbO = 24 molecules/2 = 12

Pb = 3*12 = 36 MoleculesPb = 3*12 = 36 Molecules

End notes for Thursday, November 2, 2006End notes for Thursday, November 2, 2006End notes for Thursday, November 2, 2006End notes for Thursday, November 2, 2006

Types of Chemical ReactionsTypes of Chemical Reactions

Synthesis ReactionSynthesis Reaction

Decomposition ReactionDecomposition Reaction

Single Displacement ReactionSingle Displacement Reaction

Double Displacement ReactionDouble Displacement Reaction

Combustion ReactionCombustion Reaction

Synthesis ReactionsSynthesis ReactionsAddition reactionAddition reactionTwo or more substances chemically Two or more substances chemically

combine to form ONE productcombine to form ONE product

A + B A + B C C

4Al + 3O4Al + 3O22 2Al2Al22OO33

4Fe + 3O4Fe + 3O22 2Fe2Fe22OO33

Decomposition ReactionsDecomposition ReactionsBreakdown ReactionBreakdown ReactionONE reactant breaks down into two or ONE reactant breaks down into two or

more substancesmore substances

AB AB A + B A + B

2KClO2KClO33 2KCl + 3O 2KCl + 3O22

2NaH(CO2NaH(CO33)) 2Na(CO 2Na(CO33) + H) + H22

Single Displacement ReactionsSingle Displacement ReactionsOne ELEMENT replaces another in a One ELEMENT replaces another in a

compoundcompound

A + BC A + BC AC + B AC + B

Ca + 2Ag(NOCa + 2Ag(NO33)) 2Ag + Ca(NO 2Ag + Ca(NO33))22

Fe + CuClFe + CuCl22 FeCl FeCl22 + Cu + Cu

Double Displacement ReactionsDouble Displacement Reactions The CATION of one compound replaces the The CATION of one compound replaces the

CATION of another compoundCATION of another compound TWO compounds produce two NEW TWO compounds produce two NEW

COMPOUNDSCOMPOUNDS Usually produces a PRECIPITATE (something not Usually produces a PRECIPITATE (something not

soluble in water) & a liquid/gassoluble in water) & a liquid/gas

AB + CD AB + CD AD + CB AD + CB

HCl + NaFHCl + NaF HF + NaClHF + NaCl

NaCl + KBr NaBr + KClNaCl + KBr NaBr + KCl

Combustion ReactionsCombustion ReactionsA CARBON compound combines with A CARBON compound combines with

OXYGEN to form CARBON DIOXIDE and OXYGEN to form CARBON DIOXIDE and WATERWATER

CARBON CARBON

COMPOUND + OCOMPOUND + O22 COCO22 + H + H22OO

CHCH44 + 2O + 2O22 2H2H22O + COO + CO22

Energy in ReactionsEnergy in ReactionsEnergy is released or absorbed in ALL Energy is released or absorbed in ALL

chemical reactionschemical reactions

When bonds are FORMED, energy is When bonds are FORMED, energy is RELEASEDRELEASED

When bonds are BROKEN, energy is When bonds are BROKEN, energy is ABSORBED (Taken In)ABSORBED (Taken In)

Exothermic ReactionsExothermic Reactions

Energy is RELEASEDEnergy is RELEASED

Usually occurs in the form of HEAT Usually occurs in the form of HEAT because BONDS ARE BROKENbecause BONDS ARE BROKEN

More bonds are FORMED than More bonds are FORMED than brokenbroken

Exothermic ReactionsExothermic Reactions

Energy will be on the PRODUCT side Energy will be on the PRODUCT side of the chemical equationof the chemical equation

Temperature Rises (Feels Warmer)Temperature Rises (Feels Warmer)

Examples:Examples: Burning of GasolineBurning of Gasoline Heat PacksHeat Packs Explosion of DynamiteExplosion of Dynamite

Endothermic ReactionsEndothermic ReactionsEnergy is ABSORBED (Taken in)Energy is ABSORBED (Taken in)

More bonds are BROKEN than formedMore bonds are BROKEN than formed

Temperature Drops (Feels Cold)Temperature Drops (Feels Cold)

Energy is on the REACTANT side of the Energy is on the REACTANT side of the chemical equationchemical equation

Examples:Examples: Ice packIce pack

Chemical Reactions in the AirChemical Reactions in the Air

Chlorofluorocarbons (CFCs)Chlorofluorocarbons (CFCs)Released into the atmosphere through the Released into the atmosphere through the

use of air conditioners, forest fires, volcanos, use of air conditioners, forest fires, volcanos, and other daily activitiesand other daily activities

Once released, CFCs decompose and yield Once released, CFCs decompose and yield Chlorine atoms, which destroy the ozone Chlorine atoms, which destroy the ozone layerlayer

CFCF22ClCl22 CFCF22 + Cl + Cl22

chemical equations unit 3 module 1

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