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Types of Chemical Reactions

Types of Chemical Reactions. I. Single replacement reaction II. Double replacement reaction III. Combination (synthesis) reaction IV. Decomposition reaction V. Combustion reaction. I. Single Replacement Reactions. atoms of one element replace atoms of a second element in a compound

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Types of Chemical Reactions

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  1. Types of Chemical Reactions I. Single replacement reaction II. Double replacement reaction III. Combination (synthesis) reaction IV. Decomposition reaction V. Combustion reaction

  2. I. Single Replacement Reactions • atoms of one element replace atoms of a second element in a compound • a more reactive metal will replace any metal of less reactivity

  3. Mg(NO3)2 + Zn • Examples of single replacement reactions: Mg +Zn(NO3)2 Mg + 2AgNO3 Mg(NO3)2 +2Ag Mg + LiNO3 NR

  4. II. Double Replacement Reactions • positive ions switch • generally involve two ionic compounds in aqueous solution • are characterized by the production of a precipitate • and….

  5. one of the following is true: • one product is only slightly soluble and precipitates from solution: Na2S(aq) +Cd(NO3)2(aq) CdS(s) + 2NaNO3(aq) • one product is a gas that bubbles out of the mixture: 2NaCN(aq) + H2SO4(aq) 2HCN(g) +Na2SO4(aq) • one product is a molecular compound such as water: Ca(OH)2(aq) + 2HCl(aq) CaCl2(aq) + 2H2O(l)

  6. (What about these guys?) precipitate! Double replacement reactions in aqueous solutions • most ionic compounds separate into cations and anions when dissolved in water (aqueous) • complete ionic equation - shows dissolved ionic compounds as their free ions: Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) AgCl(s) + Na+(aq) + NO3-(aq)

  7. spectator ions! How do you know which one will make the precipitate? They’re called…. • Spectator ions appear in both sides of the equation, but are not directly involved in the reaction. Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) AgCl(s) + Na+ + NO3-(aq)

  8. Copy the solubility rules from the chart on page 227. • Practice predicting the formation of a precipitate: (write the products and circle the ppts.) H2SO4 + BaCl2 2HCl + BaSO4 Al2(SO4)3 + 6NH4OH 2Al(OH)3 + 3(NH4)2SO4 2AgNO3 + H2S 2HNO3 + Ag2S CaCl2 +Pb(NO3)2 PbCl2+ Ca(NO3)2 Ca(NO3)2 + Na2CO3 CaCO3 + 2NaNO3

  9. III. Combination (synthesis) reactions: • two or more substances combine to form a single substance • reactants can be two elements or two compounds • product is always a compound

  10. 5 possibilities: • Group A metal + non-metal: compound is cation + anion 2K(s) + Cl2(g) 2KCl(s) • non- metal + non-metal: more than 1 combination is possible S(s) + O2(g) SO2(g) 2S(s) + 3O2(g) 2SO3(g)

  11. transitional metal + non-metal: more than one product possible Fe(s) + S(s) FeS(s) 2Fe(s) + 3S(s) Fe2S3(s) • some non-metals + water: acid SO2(g) + H2O(l) H2SO3(aq) • metallic oxide + water: base CaO(s) + H2O(l) Ca(OH)2(aq)

  12. ?? Why is energy required for decomposition reactions?? IV. Decomposition reactions • Compound breaks down into two simpler compounds (two or more products) CaCO3 CaO(s) + CO2(g) Explosions are the result of extremely rapid decomposition reactions!

  13. V. Combustion Reactions • an element or compound reacts with oxygen, producing energy as heat and light • usually involve carbon and hydrogen with oxygen; large amounts of heat are released (fossil fuels) CxHx + O2→CO2 + H2O *other elements (such as S and Mg) react with O2 to form combustion reactions: 2Mg(s) + O2(g)→ 2 MgO(s)

  14. Summary of reactions: • Single-replacement reaction: • Combination reaction: X + TY XY + T • Double-replacement reaction: X+Y- + R+S- X+S- + R+Y- X + Y XY • Decomposition reaction: XY X + Y • Combustion reaction: CH + O2 CO2 + H2O

  15. How do you know if a chemical reaction has occurred? • change in temperature • change in color • a gas is produced • an odor is formed • a solid is formed It’s like a baby’s diaper!

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