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Chapter 11 Chemical Reactions

Chapter 11 Chemical Reactions. 3 ways to write a Chemical Reaction Section 11.1. Word Equation Skeleton Equation – Formula Equation Balanced Chemical Equation (BCE). Word Equations. Describe chemical reactions using words with limited symbols.

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Chapter 11 Chemical Reactions

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  1. Chapter 11Chemical Reactions

  2. 3 ways to write a Chemical ReactionSection 11.1 • Word Equation • Skeleton Equation – Formula Equation • Balanced Chemical Equation • (BCE)

  3. Word Equations • Describe chemical reactions using words with limited symbols. • Requires only limited Chemistry understanding to write.

  4. Skeleton Equation – Formula Equations • Equations that show just the formulas of the reactants and products • Does NOT indicate the amounts of reactants required or resulting products • YOU MUST KNOW • Chapter 9 Chemical Names & Formulas  • 7 diatomic elements: H2,O2, N2, F2, Cl2, Br2, I2

  5. Chemical Equation Symbols (page 323 )

  6. Balanced Chemical Equations (BCE) • Law of Conservation of Mass: Mass is never created or destroyed in a chemical reaction. • BCE is the best description of a chemical reaction • Uses COEFFICIENTS to illustrate the amount of reactants and products involved in the reaction • Coefficients are LARGE numbers in front of a formula H2(g) + O2 (g) → H2O (l) skeleton 2H2(g) + 1O2 (g) → 2H2O (l) BCE Usually a coefficient of 1 is not written and just understood

  7. HOW 2 GET 2 BCE • Start with a correct skeleton equation • Most errors occur in this step • If you can’t get an equation to balance check that all formulas were written correctly in this step • Use Coefficients to follow the Law of Conservation of Mass • The number and types of atoms must be the same on both sides of the equation • Never change the subscripts of a formula to balance an equation • Hint:Start by balancing oxygen or another diatomic element • Hint: Make odds even by using a coefficient of 2 • Hint: Balance oxygen last in a combustion reaction • CO2 & H20 are products • Hint: If it is not working see errors from step 1

  8. Examples Word Equation: Iron + Oxygen → Iron (III) oxide Skeleton Equation:Fe (s) + O2 (g) → Fe2O3(s) Word Equation:Hydrogen peroxide→ Water +Oxygen Skeleton Equation: H2O2 (aq) → H2O(l) + O2(g) Word: Methane + Oxygen → Carbon dioxide + Water Skeleton: CH4(g) + O2 (g) → CO2(g) + H20(l)

  9. BCE Examples • Fe (s) + O2 (g) → Fe2O3(s) Hint: Start by balancing oxygen or another diatomic element Hint: Make odds even by using a coefficient or 2 Hint: Balance oxygen last in a combustion reaction CO2 & H20 are products Hint: If it is not working see errors from step 1 4 Fe (s) + 3 O2 (g) → 2 Fe2O3(s) Fe (s) + O2 (g) → 2 Fe2O3(s) Fe (s) + 3 O2 (g) → 2 Fe2O3(s) • H2O2(aq) → H2O (l) + O2(g) H2O2(aq) → 2H2O (l) + O2(g) 2 H2O2(aq) → 2 H2O (l) + O2(g) • CH4(g) + O2 (g) → CO2 (g)+ H20 (l) 1 CH4(g) + O2 (g) → 1 CO2 (g)+ H20 (l) 1 CH4(g) + O2 (g) → 1 CO2 (g)+ 2 H20 (l) 1 CH4(g) +2 O2 (g) → 1CO2 (g)+ 2 H20 (l) 1 CH4(g) + O2 (g) → CO2 (g)+ H20 (l)

  10. Changing the Rate of the Reaction • Catalyst • A substance that speeds up the rate reaction • It is chemically unchanged at the end of the reaction • Written above the reaction arrow • Ex: • Animation • Inhibitor • A substance that slowsthe rate of reaction. • Sometimes they even stop the reaction completely

  11. 5 Types of Chemical ReactionsSection 11.2 • Combination/Synthesis (S) • Decomposition (D) • Single Replacement (SR) • Double Replacement (DR) • Combustion (C)

  12. Combination Reaction – Synthesis • A chemical reaction where 2 or more reactants are joined to form a single product • A + B → AB • Reactants can be elements or compounds 2K(s)+ Cl2(g) 2KCl(g) 2Mg(s)+ O2(g) 2MgO(s)

  13. Decomposition Reactions • A chemical reaction where a single reactant is broken down into 2 or more simpler products • AB → A + B • Products can be elements or compounds KClO4 →KCl + 2O2 Potassium perchlorate decomposes and releases oxygen. The oxygen is used to speed up the combustion of material it is in contact with. Potassium perchlorate is used in fireworks. Ammonium dichromate decomposes to nitrogen water & chromium (III) oxide

  14. Combination & Decomposition • Combination & Decomposition reactions are opposite each other. • Combination A + B → AB • Decomposition AB → A + B

  15. + Cl Cu +2 Ag Single Replacement ReactionsSingle Displacement • A chemical reaction in which a single, free element takes the place of a less active element in a compound, setting the less active element free • A + BC AC + B • “A” can be a metal or nonmetal Formula Equation AgCl(aq) + Cu(s) CuCl2(aq) + Ag(S) Cu +1 Cl Cu +2 Ag Ag + Cl • Cl2+ NaBrNaCl + Br2

  16. Activity Series Metal Activity Series • Not every single replacement (SR) reaction will occur • An activity seriesis a list of substances ranked in order of relative reactivity • The most active metals are at the top of the table; the least active are at the bottom. • The activity series is a useful guide for predicting the products of single replacement reactions • There is an activity series for nonmetals as well Nonmetal Activity Series

  17. Double Replacement ReactionDouble Displacement • A Chemical reaction where two compounds swap ions to form two new compounds • AB + CD  AD + CB • Two Types • Both reactants are ionic solutions • Acid/BaseNeutralization reactions (Ch 19) • Will only occur if a gas, water or a precipitate(ppt) can be formed. • Precipitate is a solid that forms out of solution • Examples 1234 (formula equations) • AgNO3(aq) + NaOH(aq) AgOH(s) + NaNO3(aq) • NaOH(aq) + CoCl2(aq) Co(OH)2(s) + NaCl(aq) • NaI(aq) HgCl2 (aq) HgI2(s) + NaCl(aq) • AgNO3(aq) +NaCl(aq) AgCl(s) + NaNO3(aq)

  18. K K K KI(aq) + Pb(NO3)2(aq) PbI2(s)+ KNO3(aq) KI(aq) + Pb(NO3)2(aq)PbI2(s)+ KNO3(aq) 2 KI(aq) + Pb(NO3)2(aq)PbI2(s)+ 2 KNO3(aq) K I Pb Pb  + + I I I N N N N O O O O O O O O O O O O

  19. Combustion Reactions • An exothermic chemical reaction burning a fuel in the presence of oxygen producing carbon dioxide and water • CxHy + O2 CO2 + H2O CH4(g) + 2O2(g) CO2(g) + 2H2O(g) C10H8 + 12 O2 → 10 CO2 + 4 H2O

  20. 5 types Summary • 5 types of reactions http://i1.ytimg.com/vi/tE4668aarck/default.jpg&imgrefurl=http://www.youtube.com/user/blythex&usg=__HkRt2b8BC5v0-5dV0ROwhq5WeWE=&h=90&w=120&sz=2&hl=en&start=88&um=1&tbnid=CWQR40FL2CiA5M:&tbnh=66&tbnw=88&prev=/images%3Fq%3Dsingle%2Bdisplacement%2Breactions%26ndsp%3D18%26hl%3Den%26rls%3Dcom.microsoft:en-us:IE-SearchBox%26rlz%3D1I7GGLL_en%26sa%3DN%26start%3D72%26um%3D1

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