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CHEMICAL REACTIONS

What is a cation afraid of? A dogion !. CHEMICAL REACTIONS. CH. 11. Prior Knowledge Activity. C 6 H 12 O 6 + O 2 → CO 2 + H 2 O

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CHEMICAL REACTIONS

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  1. What is a cation afraid of? A dogion! CHEMICAL REACTIONS CH. 11

  2. Prior Knowledge Activity • C6H12O6 + O2→ CO2 + H2O • Write down everything you know about it including compounds involved and how many atoms of each element are in each molecule, names, etc... Balance the equation.

  3. Describing a Chemical Reaction Indications of a Chemical Reaction • Evolution of heat, light, and/or sound • Production of a gas • Formation of a precipitate • Color change

  4. Signs of Chemical Reactions There are five main signs that indicate a chemical reaction has taken place: release input change in color change in odor production of new gases or vapor input or release of energy difficult to reverse

  5. Word Equations • Reactants Products • Iron + oxygen iron(III) oxide • (yields, forms, produces, etc…) • *Burning a substance typically requires oxygen, so methane and oxygen are the reactants. The products are water and carbon dioxide. Write the word equation: • *

  6. Chemical Equations • Chemical equation = a representation of a chemical reaction • Skeleton equation = a chemical equation that does not indicate the relative amounts of the reactants and products • States of substances – (s) = solid, (l) = liquid, (g) = gas, (aq) = substance in aqueous solution (dissolved in water ) • Fe(s) + O2(g) → Fe2O3(s) • Catalyst = a substance that speeds up the reaction but is not used up in the reaction • H2O2(aq) H2O(l) + O2(g) *Say the word equation • Don’t forget diatomic molecules (HOBrFINCl twins or the BrINClHOF brothers) MnO2

  7. *C.P. 11.1 pg. 324 • *P.P. 1-2 pg. 324

  8. Balancing Chemical Equations • Balanced equation = each side of the equation has the same number of atoms of each element and mass is conserved • Coefficients = small whole numbers that are placed in front of the formulas in an equation in order to balance it • 1. write the skeleton equation • 2. use coefficients to balance the equation so it obeys the law of conservation of mass

  9. Cl H H H Cl Cl Cl H reactants products reactants products H H Cl Cl Unbalanced and Balanced Equations H Cl Cl Cl H H H2 + Cl2 2 HCl (balanced) (unbalanced) H2 + Cl2 HCl 2 1 2 2 1 2 2 2

  10. Hints and Steps to Balancing Chemical Equations • 1. Start at the ugliest or muddiest formula first • 2. Leave the ‘lonely’ formulas to the end, you can always put any number in front of those • 3. Treat polyatomic ions like one unit, don’t treat each atom by itself • 4. It’s a game of Trial and Error • 5. Have to have same amount of atoms of each element on the left as the right • 6. Even/odd – make them all even (sometimes doubling everything will do the trick) • 7. Coefficients must be lowest whole number ratio

  11. Practice • C.P. 11.2, P.P. 3-4 pg. 327 • C.P. 11.3, P.P. 5-6 pg. 328 • **CaSiO3 + HF → CaF2 + SiF4 + H2O • HCl + HNO3 → HOCl + NO + H2O • Li2O2 + CO2 → Li2CO3 + O2 • Ag2S + Al → Ag + Al2S3 • aluminum sulfate + calcium hydroxide → aluminum hydroxide + calcium sulfate • Phosphoric acid + sodium hydroxide yields sodium phosphate and water • CuCl2 + Al → AlCl3 + Cu • Dicarbondihydride reacts with oxygen to form carbon dioxide and water • 11.1 sect. assess. Pg. 329

  12. Types of Chemical Reactions • 6 Types of chemical reactions • Sometimes a reaction can fit into two categories • 1) Combination (synthesis) • 2) Decomposition • 3) Single-replacement • 4) Double-replacement • 5) Combustion • 6) Neutralization A + B  AB AB  A + B A + BC  AC + B AB + CD  AD + CB CH + O2 CO2 + H2O HX + BOH  BX + HOH

  13. Synthesis (combination) A + B  AB • Combination = a chemical change in which two or more substances react to form a single new substance • Metal and nonmetal • 2Mg(s) + O2(g) → 2MgO(s) • Two nonmetals (more than 1 product possible) • S(s) + O2(g) → SO2(g) • 2S(s) + 3O2(g) → 2SO3(g) • Transition metal and nonmetal (more than 1) • Fe(s) + S(s) → FeS(s) • 2Fe(s) + 3S(s) → Fe2S3(s) • *C.P. 11.4, P.P. 13-14 pg. 331

  14. Decomposition AB  A + B • Decomposition reaction = a chemical change in which a single compound breaks down into two or more simpler products • 1 reactant and two or more products • 2HgO(s) → 2Hg(l) + O2(g) • Tips for decomposition: • 1. metal hydroxides always decompose to metal oxide and H2O • 2. Most binary compounds will break down into their elements • Exception: PbO2 → PbO + O2 • 3. All carbonates (CO3) break down to the oxide and CO2 • 4. Chlorates (ClO3) break down to binary salt and O2 • C.P. 11.5, P.P. 15-16 pg. 332

  15. A + BC  AC + B Single-replacement • Single-replacement = a chemical change in which one element replaces a second element in a compound • Both the reactants and products consist of an element and a compound • 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) • Zn(s) + Cu(NO3)2(aq) → Cu(s) + Zn(NO3)2(aq) • Whether one metal will displace another metal from a compound depends upon the relative reactivities of the two metals • As a rule (not always), transition metals have the same oxidation number in a reaction: EX: Fe+2 + Cu+2(OH)2 → • Activity series = lists metals in order of decreasing reactivity • A reactive metal will replace any metal listed BELOW it in the activity series • Also works for halogens as well • Br2(aq) + NaI(aq) → NaBr(aq) + I2(aq) • Br2(aq) + NaCl(aq) → No Reaction (NR) • *C.P. 11.6, P.P. 17 pg. 334

  16. Predict if these reactions will occur 2 Al + MgCl2 3 2 3 Mg + AlCl3 Can magnesium replace aluminum? YES, magnesium is more reactive than aluminum. Activity Series No reaction Al + MgCl2 Can aluminum replace magnesium? NO, aluminum is less reactive than magnesium. Therefore, no reaction will occur. Activity Series Order of reactants DOES NOT determine how they react. No reaction MgCl2 + Al The question we must ask is can the single element replace its counterpart? metal replaces metal or nonmetal replaces nonmetal.

  17. Element Reactivity Li Rb K Ba Ca Na Mg Al Mn Zn Cr Fe Ni Sn Pb H2 Cu Hg Ag Pt Au Halogen Reactivity F2 Cl2 Br2 I2

  18. AB + CD  AD + CB Double-Replacement • Double-replacement reaction = a chemical change involving an exchange of positive ions between two compounds • For this to occur, usually one of the following is produced: a molecular compound like water, a gas, or a slightly soluble precipitate • Ca(OH)2(aq) + 2HCl(aq) → CaCl2(aq) + 2H2O(l) • 2NaCN(aq) + H2SO4(aq) → 2HCN(g) + Na2SO4(aq) • Na2S(aq) + Cd(NO3)2(aq) → CdS(s) + 2NaNO3(aq) • *C.P. 11.7, P.P. 18-19 pg. 335

  19. Combustion CH + O2 CO2 + H2O • Combustion reaction = a chemical change in which an element or a compound reacts with oxygen, often producing energy in the form of heat and light • Usually a hydrocarbon and oxygen react to produce carbon dioxide and water • 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l) • 2Mg(s) + O2(g) → 2MgO(s) • S(s) + O2(g) → SO2(g) • *C.P. 11.8, P.P. 20-21 pg. 337 • *11.2 sect. assess. 22-27 pg. 339

  20. HX + BOH  BX + HOH Neutralization • Neutralization = a chemical reaction in which an acid and a base react to form a salt. • Water is frequently produced as well. • HCl + NaOH → NaCl + H2O

  21. Net Ionic Equations • Complete ionic equation = an equation that shows dissolved ionic compounds as dissociated free ions • Net ionic equation = an equation for a reaction in solution that shows only those particles that are directly involved in the chemical change

  22. Cont… • Spectator ion = an ion that appears on both sides of an equation and is not directly involved in the reaction • A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge • *C.P. 11.9, P.P. 28 pg. 343

  23. Na2CO3 FeCO3 FeCl2 NaCl + + (aq) (ppt) Predict if a reaction will occur when you combine aqueous solutions of iron (II) chloride with aqueous sodium carbonate solution. If the reaction does occur, write a balanced chemical equation showing it. (be sure to include phase notation) Balanced chemical equation iron (II) carbonate iron (II) chloride + sodium carbonate + sodium chloride CO32- CO32- Na1+ Fe2+ Fe2+ Cl1- Cl1- Na1+ CO3 FeCO3 Na2 Cl2 Fe NaCl (aq) (ppt) Using a SOLUBILITY TABLE: sodium chloride is soluble iron (II) carbonate is insoluble 2 (aq) (aq) Complete Ionic Equation Fe2+(aq) + 2Cl1-(aq) + 2Na1+(aq) + CO32-(aq) 2Na1+(aq) + 2Cl1-(aq) + FeCO3(s)

  24. Predicting the Formation of a Precipitate • You can predict the formation of a precipitate by using the general rules for solubility of ionic compounds • *11.3 Sect. Assess. Pg. 344 If you're not part of the solution, you're part of the precipitate.

  25. chromate hydroxide carbonate bromide chloride sulfide sulfate nitrate phosphate iodide acetate Legend SOLID SOLID AQUEOUS i = insoluble ss = slightly soluble s = soluble d = decomposes n = not isolated

  26. Bellringer 1 • Balance the following chemical equations • 1. (NH4)3PO4+ Pb(NO3)4 →Pb3(PO4)4 + NH4NO3 • 2. ammonia mixes with oxygen to form nitrogen monoxide and water • 3. C2H6 + O2 →H2O + CO2 • 4. iron and sulfuric acid react to produce iron(III) sulfate and hydrogen gas • 5. BF3 + Li2SO3→ B2(SO3)3 + LiF

  27. Answers BR I • 4 + 3 → 1 + 12 • 4 + 5 → 4 + 6 • 2 + 7 → 6 + 4 • 2 + 3 → 1 + 3 • 2 + 3 → 1 + 6

  28. Bellringer 2

  29. Answers BRII

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