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 ENERGY Energy 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 + H Cl 2  Formation of a precipitate  CuSO 4 + NaOH  Cu(OH) 2 + Na 2 SO 4  Color change  HNO 3 + Cu  Cu(NO 3 ) 2 + NO 2 + H 2 O

C. Chemical Equations PbCl 2 + Na 2 CrO 4  PbCrO 4 + 2NaCl Left side are REACTANTS Right side are PRODUCTS Yields Number of moles or particles

C. Chemical Equations THE MAGNIFICENT SEVEN These elements exist in nature as diatomic molecules, never as a lone atom. H 2, N 2, O 2 F 2, Cl 2, Br 2, I 2 And Hydrogen!

C. Chemical Equations - Symbols Yields Reversible reaction (s) or ↓ as in NaCl (s) Solid or precipitate (l) as in H 2 O (l) Liquid (g) as in H 2 O (g) gas (aq) as in NaCl (aq) Aqueous i.e. dissolved in water Heat added Catalyst used

D. Balancing Equations During a process called electrolysis (electric current) water is converted to hydrogen gas and oxygen gas. H2OH2OH 2 + O 2 H O NEVER EVER CHANGE A SUBSCRIPT

D. Balancing Equations Fe 2 O 3 + H 2 SO 4 Fe 2 (SO 4 ) 3 + H 2 O Treat Polyatomic ions as one unit Fe O H SO

E. Types of reactions 1. Synthesis Reactions General Form: A + B  AB Definition: Two substances forming a new compound Mg + O 2  Fe + O 2  Assuming Fe +4 Assuming Fe +3

E. Types of reactions 2. Decomposition Reactions General Form: AB  A + B Definition: A compound breaks down into 2 or more H2OH2O HgO Ca(OH) 2  Al 2 (CO 3 ) 3  Metal hydroxides  Metal oxides and water Metal carbonates  Metal oxides and CO 2

E. Types of reactions 3. Single Replacement Reactions General Form: A + BC  B + AC OR Y + AX  X + AY Definition: A metal or halogen switches with another Al + Pb(NO 3 ) 2  Na + H 2 O  F 2 + HCl 

E. Types of reactions 4. Double Replacement Reactions General Form: AX + BY  BX + AY Definition: Two metals swap positions KI + Pb(NO 3 ) 2  FeS + HCl 

E. Types of reactions 5. Acid Base Reactions (Really a Double replacement) General Form: HX + BOH  BX + H 2 O Definition: Double replacement that makes water Acids start with H Bases end with OH HCl + NaOH 

E. Types of reactions 6. Combustion Reactions General Form: C x H y O z + O 2  CO 2 + H 2 O Definition: Hydrocarbon burns making CO 2 and H 2 O CO 2 and H 2 O are ALWAYS the products O 2 indicates combustion C 3 H 6 O 2 + O 2  C 8 H 18 + O 2 

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 K Na Cl K

F. Factors that influence Reaction rate Na Cl K

F. Factors that influence Reaction rate Four major influences: Temperature Increase speeds up reactions Faster particles (more KE) Concentration Higher concentration speeds up reactions More chances to collide Surface area Higher SA speeds up reactions More chances to collide Catalyst Addition of speeds up reactions Lowers activation energy

F. Iodine Clock Reaction

G. Activity Series Li React with cold water and acids, replacing hydrogen. React with oxygen forming oxides. TABLE OF HALOGENS RbF2 KCl2 BaBr2 SrI2 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