Chemical Chemical ReactionsReactions

Applied ChemistryApplied Chemistry

Chemical ReactionChemical ReactionChemical reactionChemical reaction – The type of – The type of

reaction in which the properties of the reaction in which the properties of the reactantsreactants are different from the are different from the productsproducts..

Chemical ChangeChemical Change – A change that – A change that produces new substances with new produces new substances with new propertiesproperties and and compositionscompositions..PhysicalPhysical changes do changes do NOTNOT change the change the

identityidentity of a substance. of a substance. NuclearNuclear changes involve changes to the changes involve changes to the

nucleusnucleus. Ex) fission and fusion. Ex) fission and fusion

Signs of a chemical Signs of a chemical changechange

Change in Change in colorcolor

Formation of a Formation of a precipitateprecipitate (cloudiness, (cloudiness,

solid formed from 2 solutions)solid formed from 2 solutions)

Production of a Production of a gasgas (bubbles; fizzing) (bubbles; fizzing)

Increase or decrease in Increase or decrease in temperaturetemperature

Change or production of an Change or production of an odorodor

Chemical EquationsChemical Equations A description of a chemical reaction A description of a chemical reaction

using using symbolssymbols instead of instead of wordswords..

Parts of a Chemical Equation: Parts of a Chemical Equation: A.A. ReactantsReactants

B.B. ProductsProducts

C.C. ArrowArrow

D.D. Plus SignPlus Sign

Parts of Chemical EquationParts of Chemical EquationA. ReactantsA. Reactants

CHCH44 + O + O22 H H22O + COO + CO22

reactantsreactants productsproducts

Written on the Written on the leftleft side of the arrow side of the arrow

StartingStarting material in a chemical material in a chemical reactionreaction

Parts of Chemical EquationParts of Chemical EquationB. ProductsB. Products

CHCH44 + O + O22 HH22O + COO + CO22

reactantsreactants productsproducts

Written on the Written on the rightright side of the arrow. side of the arrow.

Newly formed substances that are Newly formed substances that are producedproduced in a chemical reaction. in a chemical reaction.

Properties are Properties are differentdifferent than those of the than those of the reactants.reactants.

Parts of Chemical EquationParts of Chemical EquationC. ArrowC. Arrow

CHCH44 + O + O22 H H22O + COO + CO22

reactantsreactants productsproducts

YieldYield sign sign

Means Means yields or producesyields or produces

Separates the Separates the reactantsreactants from the from the productsproducts..

Parts of Chemical EquationParts of Chemical EquationD. Plus signD. Plus sign

CHCH44 ++ O O22 H H22O O ++ COCO22

reactantsreactants productsproducts

Used to Used to separateseparate reactants and to reactants and to separateseparate products products

Symbols for Symbols for statesstates

HH2 2 (g)(g) + O + O2 2 (g)(g) H H22O O (l)(l)

KIKI(aq)(aq) + Pb(NO + Pb(NO33))2 2 (aq)(aq) PbI PbI22(s) (s) + KNO+ KNO33(aq)(aq)

Physical states of the reactants and products are in Physical states of the reactants and products are in parenthesis beside the formula. parenthesis beside the formula.

g: g: gasgas

l:l: liquidliquid

s:s: solidsolid

aq: aq: aqueousaqueous (dissolved in (dissolved in waterwater))

Example ReactionExample ReactionHH2 (g)2 (g) + Cl + Cl2 (g)2 (g) → HCl → HCl (g)(g)

What are the reactants? What are the reactants?

What are the products? What are the products?

What is the physical state of all What is the physical state of all

the substances? the substances?

H2 and Cl2

HCl

gas

CatalystsCatalysts CatalystsCatalysts are sometimes added to are sometimes added to

reactants to help reactants to help speed upspeed up a a chemical reaction. chemical reaction.

Catalysts are Catalysts are unchangedunchanged in a in a chemical reaction. They are neither chemical reaction. They are neither reactants nor products. reactants nor products.

Catalysts are written Catalysts are written aboveabove the yield the yield sign.sign.

22

MnO2 2 2H O H O + O

Law of Conservation of Law of Conservation of MassMass Mass is neither Mass is neither createdcreated nor nor destroyeddestroyed in a in a

chemical reaction, it can only chemical reaction, it can only changechange formform.. Mass of the reactants is the Mass of the reactants is the SAMESAME as the mass as the mass

of the products.of the products. The number of each type of atom in the The number of each type of atom in the

reactants must be reactants must be equalequal to the number of to the number of atoms in the atoms in the productsproducts..

Since the number of atoms is the same, the Since the number of atoms is the same, the massmass will be the same on both sides of the will be the same on both sides of the reaction.reaction.

Also, the Also, the typestypes of elements will be the same of elements will be the same on each side.on each side.

Balancing EquationsBalancing EquationsHH2 (g)2 (g) + Cl + Cl2 (g)2 (g) → HCl → HCl (g) (g)

Reactant sideReactant side Product sideProduct side

# of H atoms = 2# of H atoms = 2 # of H atoms = 1# of H atoms = 1

# of Cl atoms = 2# of Cl atoms = 2 # of Cl atoms = 1# of Cl atoms = 1

Does this equation have the same number of atoms Does this equation have the same number of atoms of each element on both sides of the equation? of each element on both sides of the equation?

Therefore, it Therefore, it does notdoes not follow the Law of follow the Law of Conservation of Mass. Conservation of Mass.

NO!!!

Balancing Equations Balancing Equations (cont.)(cont.)

HH2 (g)2 (g) + Cl + Cl2 (g)2 (g) → HCl→ HCl(g) (g)

This equation is called a This equation is called a skeletonskeleton equation.equation.

This equation must be This equation must be balancedbalanced with with coefficientscoefficients (the number in front of a (the number in front of a formula for a substance).formula for a substance).

a BALANCED a BALANCED Equation…Equation…

HH2 (g)2 (g) + Cl + Cl2 (g)2 (g) → → 22HClHCl(g)(g)

Reactant sideReactant side Product sideProduct side

# of H atoms = 2# of H atoms = 2 # of H atoms = # of H atoms = 22

# of Cl atoms = 2# of Cl atoms = 2 # of Cl atoms = # of Cl atoms = 22

A coefficient of 1(one) is understood and is not A coefficient of 1(one) is understood and is not necessary in the balanced chemical equation.necessary in the balanced chemical equation.

Steps for balancing Steps for balancing equationsequations

1.1. Write the chemical formula for each Write the chemical formula for each reactant and product.reactant and product.

2.2. Indicate the state of each substance.Indicate the state of each substance.

3.3. Use Use coefficientscoefficients in front of the in front of the substance to balance the equation. substance to balance the equation. The The number of each number of each atomatom should should be the be the SAMESAME on both sides of the on both sides of the equation.equation.

NOTE: NOTE: NEVERNEVER CHANGE SUBSCRIPTS!!! CHANGE SUBSCRIPTS!!!

Balancing ExamplesBalancing Examples1.1. HH22 + Br + Br22 → → 22HBrHBr

2.2. 22Na + ClNa + Cl22 → → 22NaClNaCl

3.3. 44Na + ONa + O22 → → 22NaNa22OO

4.4. Zn + Zn + 22HCl → ZnClHCl → ZnCl22 + H + H22

5.5. 44Fe + Fe + 33OO22 → → 22FeFe22OO33

Balancing ExamplesBalancing Examples6.6. PP44

+ + 55OO22 → → 22PP22OO55

7.7. AlAl22OO33 + + 33HH22 → → 22Al Al + + 33HH22OO

8.8. 22Ca + OCa + O2 2 → → 22CaOCaO

9.9. 33ClCl22 + + 22AlBrAlBr33 → → 33BrBr22 + + 22AlClAlCl33

10.10. 22HgO → HgO → 22Hg + OHg + O22

Synthesis ReactionsSynthesis Reactions

Two or more reactants produce Two or more reactants produce ONEONE productproduct

A.K.A. A.K.A. Direct combinationDirect combination reactants reactants

Follows the pattern: Follows the pattern: A + B A + B → AB→ AB**only **only ONEONE product** product**

NN22 + 3H + 3H22 → 2NH→ 2NH33

22 reactants reactants → → 11 product product

Synthesis ReactionSynthesis Reaction

Combustion Combustion ReactionsReactions

Chemical reaction involving Chemical reaction involving oxygen (Ooxygen (O22)) in which in which lightlight and and heatheat are produced. are produced. Heat is a useful product. Heat is a useful product.

When fuels are burned in the presence of When fuels are burned in the presence of oxygen, oxygen, water (Hwater (H22O)O) and and carbon carbon dioxide (COdioxide (CO22)) are often produced. are often produced.

Follows the pattern: BC + A Follows the pattern: BC + A → BA + CA→ BA + CA

CHCH4 (g)4 (g) + 2O + 2O2 (g)2 (g) → CO → CO2 (g)2 (g) + 2H + 2H22OO(g)(g) + + heatheat

Combustion ReactionCombustion Reaction

Decomposition Decomposition ReactionsReactions

Opposite of Opposite of synthesissynthesis reactions reactions Substance breaks down into Substance breaks down into simpler simpler

substances.substances. Chemists can cause decomposition, but Chemists can cause decomposition, but

decomposition can also be decomposition can also be spontaneousspontaneous..

AB AB → A + B→ A + B

Only Only ONEONE reactant! reactant!

2H2H22O → 2HO → 2H22 + O + O22

11 reactant → reactant → 22 productsproducts

Single Displacement Single Displacement (Replacement) Reactions(Replacement) Reactions

Change in Change in bonds.bonds.One substance will One substance will replacereplace, or , or bump bump

outout, another element in a compound., another element in a compound.

AA + + BBC C → → AAC + C + BB(2 reactants – element and compound(2 reactants – element and compound2 products – element and compound)2 products – element and compound)

ZnZn + + HH22SOSO44 → → ZnZnSOSO44 + + HH22

Double Displacement Double Displacement (Replacement) Reactions(Replacement) Reactions

Both substances change Both substances change partnerspartners

AABB + + CCDD → → AADD + + CCBB

22KKII(aq)(aq) + + PbPb(NO(NO33))22 (aq)(aq) 22KKNONO33(aq)(aq) + + PbPbII22(s) (s)

2 reactants (both compounds) and 2 reactants (both compounds) and 2 products (both compounds)2 products (both compounds)

Synthesis

Decomposition

SR

DR

Energy Changes in Energy Changes in ReactionsReactions

ExothermicExothermic Reactions Reactions ReleaseRelease heat into the surroundings heat into the surroundings

Surroundings will get Surroundings will get hotterhotter..

Sometimes need heat to them started.Sometimes need heat to them started.

A noticeable A noticeable increaseincrease in temperature in temperature occurs. occurs.

Ex. Ex. Combustion & Burning MgCombustion & Burning Mg

Energy Changes in Energy Changes in ReactionsReactions

EndothermicEndothermic Reactions Reactions AbsorbAbsorb heat from the surroundings. heat from the surroundings.

Surroundings will get Surroundings will get coolercooler. .

Need heat to keep them going.Need heat to keep them going.

A noticeable A noticeable decreasedecrease in temperature in temperature occurs.occurs.

Ex. Ex. Photosynthesis and cold packsPhotosynthesis and cold packs

The reactivity of a metal is based on its The reactivity of a metal is based on its ability to ability to replacereplace another in a compound. another in a compound. The metal is oxidized. The metal is oxidized.

If a single replacement reaction occurs, the If a single replacement reaction occurs, the metal that “cuts in” is metal that “cuts in” is MOREMORE reactive than reactive than the one that was removed or replaced.the one that was removed or replaced.

An An activity seriesactivity series of metals is a listing of metals is a listing that ranks metals according to their that ranks metals according to their reactivityreactivity.. The The most most active metal is at the active metal is at the TOPTOP of the list of the list The The least least active metal is at the active metal is at the BOTTOMBOTTOM of the of the

listlist

Reactivity or Activity of Reactivity or Activity of MetalsMetals

The The ACTIVITY SERIESACTIVITY SERIES is listed below is listed below::lithiumlithiumpotassiumpotassiumbariumbariumstrontiumstrontiumcalciumcalciumsodiumsodiummagnesiummagnesiumaluminumaluminummanganesemanganesezinczincironironcadmiumcadmiumcobaltcobaltnickelnickeltintinleadleadhydrogenhydrogencoppercoppersilversilvermercurymercurygoldgold

The most active metal is LITHIUM

The least active metal is GOLD

Which is more active nickel or iron? IRON

Examples of the Examples of the Activity of MetalsActivity of Metals

Al + CuClAl + CuCl22 Cu + AlCl Cu + AlCl33

Mg + HCl Mg + HCl H H22 + MgCl + MgCl22

Cu + HCl Cu + HCl No Reaction! No Reaction!

Treatment of Treatment of MetalsMetals

Metals are treated to protect from Metals are treated to protect from corrosioncorrosion or to make the metals or to make the metals better suited for specific purposes, better suited for specific purposes, such as, improving such as, improving strengthstrength or or making them making them more light weightmore light weight..

Types of Metal TreatmentsTypes of Metal TreatmentsGalvanizing Galvanizing = = coating with zinc coating with zinc

(electroplating)(electroplating)Painting = Painting = painting helps prevent painting helps prevent

corrosioncorrosionMaking Making alloysalloys = = mixture of 2/more mixture of 2/more

metals or a metal and a nonmetalmetals or a metal and a nonmetal. .

Common AlloysCommon AlloysBronzeBronzeBrassBrassSteelSteelStainless steelStainless steelPewterPewterSolderSolder

copper + tin

copper + zinc

iron + carbon

iron, carbon + chromium

lead, tin + silver

copper, tin + antimony