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Chemical Reactions

Chemical Reactions. Potassium metal reacts with chlorine gas Zn metal reacts with aqueous copper(II) sulfate Aqueous silver nitrate reacts with aqueous potassium chromate Mercury(II) oxide reacts when heated Hexane reacts with oxygen.

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Chemical Reactions

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  1. Chemical Reactions Potassium metal reacts with chlorine gas Zn metal reacts with aqueous copper(II) sulfate Aqueous silver nitrate reacts with aqueous potassium chromate Mercury(II) oxide reacts when heated Hexane reacts with oxygen Write and balance the equation and identify the reaction type for each of the following reactions:

  2. Chemical Reactions 2 major categories of inorganic chemical reactions: Double Replacement Oxidation - Reduction Precipitation Neutralization Synthesis Decomposition Single Replacement Combustion Precipitation – Driving Force is formation of Precipitate (Use solubility rules to determine) Ex: AgNO3 + K2CrO4 - Molecular -Complete ionic -Net ionic

  3. Solubility Rules • All common compounds of Group I and ammonium ions are soluble. • All nitrates, acetates, and chlorates are soluble. • All binary compounds of the halogens (other than F) with metals are soluble, except those of Ag, Hg(I), and Pb. Pb halides are soluble in hot water.) • All sulfates are soluble, except those of barium, strontium, calcium, lead, silver, and mercury (I). The latter three are slightly soluble. • Except for rule 1, carbonates, hydroxides, oxides, silicates, and phosphates are insoluble. • Sulfides are insoluble except for calcium, barium, strontium, magnesium, sodium, potassium, and ammonium. Note: All items in this color are to be memorized!

  4. Chemical Reactions You try: Write the molecular, complete ionic and net ionic equations for the reaction of aqueous aluminum sulfate with aqueous sodium hydroxide. Calculate the mass of aluminum hydroxide that could be produced if 30.0 mL of 0.150M NaOH(aq) is combined with 25.0 mL of 0.250M Al2(SO4)3 (aq) Neutralization – Arrhenius acid with Arrhenius base (driving force is the formation of H2O) Ex: HCl + NaOH -Molecular -Complete ionic -Net ionic

  5. Chemical Reactions Oxidation – Reduction (Redox) • The following is the rxn. for the formation of rust: • Fe(s) + O2(g)  Fe2O3(s) • What is the oxidation number of iron? • What is the oxidation number of iron in Fe2O3? • What happened? • Because it involved reacting with O2, corrosion of a metal was originally called oxidation. • It was later found that similar reactions occurred without O2. • Now oxidation simply means that an element has LOST electrons.

  6. Chemical Reactions • Look back at the reaction, what happened to the O2? • When an element GAINS electrons, we say that it has been reduced. • The oxidation number become less/lower. • A way to remember REDOX, is to think of a lion. • LEO goes GER In the following reaction, determine the oxidation state for each element and then determine what is reduced, oxidized; the oxidizing agent and the reducing agent: Zn + CuSO4→ ZnSO4 + Cu

  7. Assigning Oxidation States • Uncombined elements = 0 • Monatomic ions have an oxidation state equal to their charge • Including ions within compounds • e.g. Na = +1 in Na2CO3 • O = -2 as oxide, O = -1 as peroxide (O2-2) • H = +1; except in MHx , H = -1 • (where M = metal)

  8. Assigning Oxidation States • Most electronegative nonmetal in a compound has a negative oxidation state assigned; base it on position on the Periodic Table • For a neutral compound, the sum of the oxidation states = 0 • For a polyatomic ion, the sum of the oxidation states = the charge on the ion

  9. Balancing Oxidation-Reduction Reactions by the Half-Reaction Method • Write the oxidation and reduction half-reactions • For Each Half-Reaction • Balance all elements except hydrogen and oxygen • Balance O using H2O • Balance H using H+ • Balance the charge using electrons • If necessary, multiply the half-reactions to equalize the number of electrons transferred • Add the half-reactions and cancel identical species • Check to ensure elements and charges are balanced

  10. Examples • Balance the Following: • MnO4-1(aq) + Fe+2(aq) ® Fe+3(aq) + Mn+2(aq) • 2. Cr2O72-(aq) + C2H5OH(aq)  Cr3+(aq) + CO2(g)

  11. Redox Titration Analysis by titration can also be done using redox reactions that go rapidly to completion in aqueous solution. The method is the same but equivalence refers to moles of electrons transferred rather than H+ or OH-. A 1.026g sample of iron-containing ore requires 24.35 mL of 0.0195 M potassium permanganate solution to reach the equivalence point. What is the mass % of iron in the ore? 12.9% Fe Answer:

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