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Chapter 3 & 4: Reactions Part 2 Read: HW: BLB 3.1–3.2; 4.2–4.4 BLB 4:19, 24, 39, 49a, c, e, f, 51b, d Supplemental Reactions 3–5 • Combination reactions (Chapter 3) 2Mg(s) + O2(!) ! 2MgO(s) • Decomposition reactions (Chapter 3) Single Displacement Reactions • Redox reactions • Oxidation numbers PbCO3(s) !PbO(s) + CO2(g) Late drop deadline: _______________________ Check out the grade calculator on the Chem110 website or on the Angel Lessons Tab Review chemical nomenclature (SCT #5) Memorize strong acids & bases (BLB Table 4.2) Bonus deadline for Skill Check Test #10: ________ Missed Exam 1, 2 or 3? Make-up Exam: info on the website. Covers material from Exams 1–3, multiple choice. You must sign up by completing the request form & giving it to me (download the form) Page 1 • (Complete) Combustion reactions (Ch. 3.2) C3H8(g) + 5O2 (g) ! 3CO2 (g) + 4H2O(g) Know: • Exchange reactions (Metathesis) • Formation of a precipitate • Formation of a gas • Formation of a weak or non-electrolyte (neutralization) L. S. Van Der Sluys Review Patterns of reactivity Chapter 4 Reactions • Exchange reactions (Chapter 4) Precipitation Pb(NO3)2(aq) + 2KI(aq) ! PbI(s) " + 2KNO3(aq) Neutralization NaOH(aq) + HCl(aq) ! NaCl(aq) + H2O(!) Gas formation 2HCl(aq) + Na2S(aq) ! H2S(g) # + 2NaCl(aq) • Single displacement reactions (Redox: Ch. 4) 2Ca(s) + O2(g) ! 2CaO(s) L. S. Van Der Sluys Page 2 Chapter 4 Reactions Exchange Reactions: GAS FORMATION 1. direct production of a gas (EX: H2, NO2, SO2) 2. formation of a weak acid which decomposes to a gas: CO2 CO2 H 2S Single Displacement reactions (Oxidation-Reduction) Oxidation of Calcium metal by molecular O2 N2 Example: Sodium Bicarbonate Plus HCl Molecular Equation What is the Chemical Reaction?? NaHCO3(aq)+HCl(aq) ! H2CO3(aq)+NaCl(aq) " Ionic Equation Na (aq) + HCO3$ (aq) + H+(aq) + Cl$ (aq) ! H2CO3 (aq)+ Na+(aq)+Cl$ (aq) " + Na (aq) + Cl$ (aq) + CO2(g)+ H2O(l) + Net Ionic Equation L. S. Van Der Sluys Page 3 Chapter 4 Reactions !How do you know which species is being oxidized and which is being reduced?? L. S. Van Der Sluys Page 4 Chapter 4 Reactions Rules for determining Oxidation States 1. Oxidation state of atom in elemental form is zero. e.g. Cl2 O2 P4 C(s) S8 2. The oxidation number of a monatomic ion equals its charge. 3. Some elements have “common” oxidation numbers that can be used as reference in determining the oxidation numbers of other atoms in the compound. Alkali metals +1 Alkaline earth metals +2 Fluorine –1 Cl, Br, I almost always –1 O usually –2 Oxidizing agents species that is actually being reduced (gaining e–) in reaction examples of good oxidizing agents: O2, halogens, H2O2, HNO3, Cr2O7–, MnO4– peroxides (–1) & superoxides possible H usually +1 Hydrides: metal-H compounds (–1) 4. Sum of oxidation numbers is equal to overall charge of molecule or ion: • For a neutral compound the sum of oxidation numbers equals zero. • For a polyatomic ion, the sum of the oxidation numbers is equal to the charge on the ion. 5. Shared electrons are assigned to the more electronegative atom of the pair: The more electronegative atom will have a negative oxidation number. L. S. Van Der Sluys Page 5 Chapter 4 Reactions Reducing agents species that is actually being oxidized (losing e–) in reaction examples of good reducing agents: H2, C, metals L. S. Van Der Sluys Page 6 Chapter 4 Reactions Oxidation-Reduction Reactions Zn(s) + CuSO4(aq) ! ZnSO4(aq) +Cu(s) Examples of Oxidation Reduction Reactions 1. Acid + Metal What is oxidized? Mg(s) + 2HCl(aq) ! MgCl2 + H2(g) What is reduced? Ionic equation: What is the oxidizing agent? Net ionic equation: Spectator Ions: What is the reducing agent? 2. Salt + Metal Fe(s) + Ni(NO3)2(aq) ! Fe(NO3)2 + Ni(s) Ionic equation: Ionic equation: Net ionic equation: Net ionic equation Spectator Ions: L. S. Van Der Sluys Page 7 Chapter 4 Reactions L. S. Van Der Sluys Page 8 Chapter 4 Reactions Activity Series Using the Activity Series: Predicts whether a certain metal will be oxidized Oxidation causes: • destruction of the metal framework • failure of machinery • deterioration (think rust) • weakening of metal Will the metal element displace the atom from its compound in a reaction? Na(s) + H2O(l) ! Au(s) + H2O(g) ! Zn(s) + AgNO3(aq) ! Active metals (groups IA, IIA, Al) Inactive (inert metals): jewelry metals Other metals are in between. L. S. Van Der Sluys Page 9 Chapter 4 Reactions L. S. Van Der Sluys Page 10 Chapter 4 Reactions Remember: An element that is higher in the activity series will displace an element below it. Zn(s) + CuSO4(aq) ! ZnSO4(aq)+ Cu(s) Ag(s) + Cu(NO3)2(aq) ! NO REACTION Demo: Al(s) + Al(s) + L. S. Van Der Sluys CuCl2(aq) ! HCl(aq) ! Page 11 AlCl3(aq)+ Cu(s) AlCl3(aq)+ H2(g) Chapter 4 Reactions Practice Questions: 1. What is the oxidation state of Cu in CuSO4? 2. What is the oxidation state of O in CuSO4? 3. What is the oxidation state of S in CuSO4? L. S. Van Der Sluys Page 12 Chapter 4 Reactions Practice Question: What are the spectator ions for the reaction provided below? What is the net ionic reaction? 2HF + Ba(OH)2 ! 2H2O + BaF2 Practice Question: What are the spectator ions for the reaction provided below? What is the net ionic reaction? NH3 L. S. Van Der Sluys + HCl ! NH4+ Page 13 + Cl - Chapter 4 Reactions