Chapter 8: Chemical Reactions

OBJECTIVES

1. Identify when a chemical reaction occurs

2. Write chemical equations

3. Balance chemical equations

4. Predict the products of reactions when the reactants are known

5. Use the Activity series to determine if a reaction will occur

A. Energy and Chemical Reactions

_____________ Releases Energy such as heat, sound, and light. Feels Hot.

_____________ Absorbs Energy such as heat; feels cold.

ENDOTHERMIC

EXOTHERMIC

A. Energy and Chemical Reactions

ACTIVATION ENERGYEnergy needed to trigger a reaction.

EXO ENDO

B. Indications of chemical reactions

Evolution of heat and light Burning Alcohol

Formation of a gas

NaOCl + HCl NaCl + H20 + Cl2

Formation of a precipitate CuSO4 + NaOH Cu(OH)2 + Na2SO4

Color change HNO3 + Cu Cu(NO3)2 + NO2 + H2O

C. Chemical Equations

PbCl2 + Na2CrO4 PbCrO4 + 2NaCl

Left side are REACTANTS

Right side arePRODUCTS

Yields

Number of moles or particles

C. Chemical Equations

THE MAGNIFICENT SEVENThese elements exist in nature as diatomic

molecules, never as a lone atom.

H2, N2, O2 F2, Cl2, Br2, I2

And Hydrogen!

C. Chemical Equations - Symbols

Yields Reversible reaction

(s) or ↓as in NaCl (s) Solid or precipitate

(l) as in H2O (l) Liquid

(g) as in H2O (g) gas

(aq) as in NaCl (aq) Aqueous i.e. dissolved in wateroCor 75 Heat added

Pd Catalyst used

D. Balancing Equations

During a process called electrolysis (electric current) water is converted to hydrogen gas and oxygen gas.

H2O H2 + O2

H

O

2 2

21

24

2

24

NEVER EVER CHANGE A SUBSCRIPT

D. Balancing Equations

Fe2O3 + H2SO4 Fe2(SO4)3 + H2O Treat Polyatomic ions as one unit

Fe

O

H

SO4

2

2

3

1

2

1

2

3

3

3

6

3

6

3

E. Types of reactions

1. Synthesis ReactionsGeneral Form: A + B ABDefinition: Two substances forming a new compound

Mg + O2

Fe + O2

Fe + O2

Assuming Fe+4

Assuming Fe+3

E. Types of reactions

2. Decomposition ReactionsGeneral Form: AB A + BDefinition: A compound breaks down into 2 or more

H2O

HgO

Ca(OH)2

Al2(CO3)3

Metal hydroxides Metal oxides and water

Metal carbonates Metal oxides and CO2

𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦→

Δ→

E. Types of reactions

3. Single Replacement ReactionsGeneral Form: A + BC B + AC OR Y + AX X + AY

Definition: A metal or halogen switches with another

Al + Pb(NO3)2

Na + H2O

F2+ HCl

E. Types of reactions

4. Double Replacement ReactionsGeneral Form: AX + BY BX + AYDefinition: Two metals swap positions

KI + Pb(NO3)2

FeS + HCl

E. Types of reactions

5. Acid Base Reactions (Really a Double replacement)General Form: HX + BOH BX + H2O

Definition: Double replacement that makes water

Acids start with HBases end with OH

HCl + NaOH

E. Types of reactions

6. Combustion ReactionsGeneral Form: CxHyOz + O2 CO2 + H2ODefinition: Hydrocarbon burns making CO2 and H2O

CO2 and H2O areALWAYS

the products

O2 indicates combustion

C3H6O2 + O2

C8H18 + O2

F. Factors that influence Reaction rate

Reaction rate is determined by particle collisions

Successful collisions:

Collide with each other

Have the correct orientation

Have enough kinetic energy to break bonds

Na Cl KNa Cl K

F. Factors that influence Reaction rate

NaCl

K

F. Factors that influence Reaction rate

Four major influences: Temperature

Increase speeds up reactionsFaster particles (more KE)

ConcentrationHigher concentration speeds up reactionsMore chances to collide

Surface areaHigher SA speeds up reactionsMore chances to collide

CatalystAddition of speeds up reactionsLowers activation energy

F. Iodine Clock Reaction

G. Activity SeriesLi React with cold water and acids,

replacing hydrogen. React with oxygen forming oxides.

TABLE OF HALOGENS

Rb F2

K Cl2

Ba Br2

Sr I2

Ca

Na

Mg React with STEAM and acids replacing hydrogen. React with oxygen forming oxides.

Al

Mn

Zn

Cr

Fe

Cd

Co Do NOT react with water. React with acids replacing hydrogen. React with oxygen forming oxides.

Ni

Sn

Pb

H2 React with oxygen forming oxides.Sb

Bi

Cu

Hg

Ag Fairly unreactive.Pt

Au

Most Reactive

Least Reactive

H. Solubility Chart