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Slide 1 ___________________________________ 8 Chemical Equations ___________________________________ ___________________________________ ___________________________________ ___________________________________ Flames and sparks result when aluminum foil is dropped into liquid bromine. ___________________________________ Foundations of College Chemistry, 14th Ed. ___________________________________ Morris Hein and Susan Arena Copyright © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 2 ___________________________________ Chapter Outline ___________________________________ 8.1 The Chemical Equation ___________________________________ 8.2 Writing and Balancing Chemical Equations ___________________________________ 8.3 Types of Chemical Equations 8.4 Heat in Chemical Reactions ___________________________________ 8.5 Global Warming: The Greenhouse Effects ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 3 ___________________________________ Chemical Equations ___________________________________ Chemical Equations: shorthand notation for chemical changes or reactions. ___________________________________ Chemists use chemical equations to: a. Summarize a chemical reaction by displaying the substances reacting and forming. b. Indicate specific amounts of materials consumed or produced during the reaction. ___________________________________ ___________________________________ Reactants: substances consumed during the reaction. Products: substances formed during the reaction. aA + bB ___________________________________ cC + dD Atom balance must be maintained in all chemical reactions. All atoms from reactants must appear as part of products. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide ___________________________________ Chemical Equations 4 ___________________________________ General Structure of Chemical Equations: 1. Reactants and products are separated by an arrow. Reactants are on the left side of the arrow, products are on the right. aA + bB cC + dD ___________________________________ ___________________________________ Reactants Products 2. Whole number coefficients are placed in front of substances to balance the atoms in the equation. The numbers indicate the units of the substance reacted or formed during the reaction. ___________________________________ ___________________________________ ___________________________________ The coefficient 1 is not written in a balanced equation. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ Chemical Equations 5 ___________________________________ General Structure of Chemical Equations: 3. Information about the reaction (temperature, time) may be placed above or below the reaction arrow. aA + bB ∆ ___________________________________ ___________________________________ cC + dD ∆ indicates heat ___________________________________ 4. The physical state is written in brackets after the formula of the substance. ___________________________________ (g) for gas, (l) for liquid, (s) for solid, (aq) for aqueous a A (s) + b B (l) c C (g) + d D (s) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ ___________________________________ Chemical Equations 6 ___________________________________ Symbol Summary Symbol ___________________________________ Significance Produces (points towards products) (s) Solid (written after substance) (l) Liquid (written after substance) (g) Gas (written after substance) (aq) Substance dissolved in an aqueous solution ∆ ___________________________________ ___________________________________ ___________________________________ Heat is added (above or below reaction arrow) © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 7 ___________________________________ Law of Conservation of Mass ___________________________________ Law of Conservation of Mass: the total mass of substances in a chemical reaction must remain constant. ___________________________________ ___________________________________ water hydrogen + oxygen 100.0 g 11.2 g 88.8 g ___________________________________ 100.0 g total of products reactants ___________________________________ In any chemical reaction: Mass of reactants = Mass of products © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 8 ___________________________________ ___________________________________ Writing and Balancing Chemical Equations ___________________________________ Balanced chemical equations: contain the same number of each kind of atom on both sides of the equation. ___________________________________ General Method for Writing and Balancing Chemical Equations ___________________________________ 1. Identify the Reaction. Write a word equation for the reaction. mercury(II) oxide ∆ ___________________________________ mercury + oxygen ___________________________________ 2. Write the unbalanced (skeleton) equation. Write the correct formula for each substance ∆ HgO © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 9 ___________________________________ Hg + O2 ___________________________________ Writing and Balancing Chemical Equations ___________________________________ General Method for Writing and Balancing Chemical Equations ___________________________________ 3. Balance the equation. ___________________________________ a. Count the number of each atom on the reactants and products side and determine what requires balancing. ∆ HgO Hg: O: 1 1 ___________________________________ Hg + O2 Hg: O: 1 2 ___________________________________ ___________________________________ Oxygen atoms need balancing on the reactants side. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 10 ___________________________________ Writing and Balancing Chemical Equations ___________________________________ General Method for Writing and Balancing Chemical Equations ___________________________________ b. Balance each element sequentially, using whole numbers. It is often best to balance metals first. ___________________________________ ∆ 2 HgO Hg: O: 2 2 Hg + O2 Hg: O: ___________________________________ 1 2 ___________________________________ Now Hg atoms need balancing on the products side. c. Check after adding coefficients that all atoms still balance. Adjust as needed (a 2 is needed in front of Hg). © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 11 ___________________________________ ___________________________________ Writing and Balancing Chemical Equations ___________________________________ General Method for Writing and Balancing Chemical Equations ___________________________________ d. Do a final check to make sure all atoms now balance on both sides of the equation. ∆ 2 HgO Hg: O: 2 Hg + O2 Hg: O: 2 2 ___________________________________ ___________________________________ 2 2 ___________________________________ Note: always use the smallest whole numbers! 4 HgO ∆ 4 Hg + 2 O2 ___________________________________ Balanced but incorrect form! © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 12 ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for when magnesium metal undergoes combustion to produce magnesium oxide. ___________________________________ 1. Identify the Reaction. Write a word equation for the reaction. magnesium + oxygen ___________________________________ magnesium oxide ___________________________________ 2. Write the unbalanced (skeleton) equation. Write the correct formula for each substance Mg + O2 ___________________________________ MgO © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 13 ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for when magnesium metal undergoes combustion to produce magnesium oxide. ___________________________________ 3. Balance the equation. ___________________________________ a. Count the number of each atom on the reactants and products side and determine what requires balancing. Mg + O2 Mg: O: 1 2 ___________________________________ MgO Mg: O: 1 1 ___________________________________ Oxygen needs balancing on the products side. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 14 ___________________________________ ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for when magnesium metal undergoes combustion to produce magnesium oxide. ___________________________________ b. Balance each element sequentially, using whole numbers. It is often best to balance metals first. Mg + O2 Mg: O: 1 2 ___________________________________ 2 MgO ___________________________________ Mg: O: ___________________________________ 2 2 Mg now needs balancing on the reactants side. ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 15 ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for when magnesium metal undergoes combustion to produce magnesium oxide. ___________________________________ c. Check after adding coefficients that all atoms still balance. Adjust as needed (a 2 is needed in front of Mg). 2 Mg + O2 Mg: O: 2 2 ___________________________________ 2 MgO ___________________________________ Mg: O: ___________________________________ 2 2 d. Do a final check to make sure all atoms now balance on both sides of the equation. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 16 ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the decomposition of potassium chlorate upon heating to give oxygen and potassium chloride. ___________________________________ 1. Identify the Reaction. Write a word equation for the reaction. Potassium chlorate ___________________________________ potassium chloride + oxygen ___________________________________ 2. Write the unbalanced (skeleton) equation. Write the correct formula for each substance KClO3 ∆ KCl + O2 17 ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the decomposition of potassium chlorate upon heating to give oxygen and potassium chloride. ___________________________________ 3. Balance the equation. ___________________________________ a. Count the number of each atom on the reactants and products side and determine what requires balancing. KClO3 ∆ ___________________________________ KCl + O2 K: 1 K: 1 Cl: 1 Cl: 1 O: 2 O: 3 Oxygen needs balancing on both sides of the equation. 18 ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the decomposition of potassium chlorate upon heating to give oxygen and potassium chloride. ___________________________________ b. Balance each element sequentially, using whole numbers. It is often best to balance metals first. 2 KClO3 K: Cl: O: 2 2 6 ∆ ___________________________________ KCl + 3 O2 K: Cl: O: ___________________________________ 1 1 6 ___________________________________ The lowest common multiple of 2 and 3 is 6. Add coefficients as appropriate to make 6 O atoms. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 19 ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the decomposition of potassium chlorate upon heating to give oxygen and potassium chloride. ___________________________________ c. Check after adding coefficients that all atoms still balance. Adjust as needed (a 2 is needed in front of KCl). 2 KClO3 K: Cl: O: ∆ 2 2 6 ___________________________________ 2 KCl + 3 O2 K: Cl: O: ___________________________________ 2 2 6 ___________________________________ d. Do a final check to make sure all atoms now balance on both sides of the equation. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 20 ___________________________________ ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the reaction of silver nitrate with hydrogen sulfide to produce silver sulfide and nitric acid. ___________________________________ ___________________________________ 1. Identify the Reaction. Write a word equation for the reaction. silver nitrate + hydrogen sulfide ___________________________________ silver sulfide + nitric acid 2. Write the unbalanced (skeleton) equation. Write the correct formula for each substance AgNO3 + H2S Ag2S + HNO3 © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 21 ___________________________________ ___________________________________ ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the reaction of silver nitrate with hydrogen sulfide to produce silver sulfide and nitric acid. 3. Balance the equation. ___________________________________ a. Count the number of each atom on the reactants and products side and determine what requires balancing. ___________________________________ Ag2S + HNO3 AgNO3 + H2S Ag: 1 Ag: 2 H: 2 H: 1 S: 1 S: 1 NO3: 1 NO3: 1 Note: If polyatomic ions do not change, they can be balanced as a “unit”. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ ___________________________________ ___________________________________ Slide 22 ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the reaction of silver nitrate with hydrogen sulfide to produce silver sulfide and nitric acid. ___________________________________ b. Balance each element sequentially, using whole numbers. It is often best to balance metals first. 2 AgNO3 + H2S Ag: H: S: NO3: ___________________________________ Ag2S + HNO3 2 2 1 2 Ag: H: S: NO3: ___________________________________ 2 1 1 1 ___________________________________ ___________________________________ H and NO3 are now unbalanced. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 23 ___________________________________ Balancing Chemical Equations Practice ___________________________________ c. Check after adding coefficients that all atoms still balance. Adjust as needed (a 2 is needed in front of HNO3). 2 AgNO3 + H2S Ag: H: S: NO3: ___________________________________ Ag2S + 2 HNO3 2 2 1 2 Ag: H: S: NO3: ___________________________________ 2 2 1 2 ___________________________________ ___________________________________ H and NO3 are now balanced. d. Do a final check to make sure all atoms now balance on both sides of the equation. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 24 ___________________________________ ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the combustion of butane (C4H10) gas, where carbon dioxide and water are the only products. a. C4H10 + 5 O2 ___________________________________ 4 CO2 + 5 H2O b. C4H10 + O2 ___________________________________ CO2 + H2O c. 2 C4H10 + 13 O2 8 CO2 + 10 H2O d. C4H10 + 6.5 O2 4 CO2 + 5 H2O ___________________________________ 1. Identify the Reaction. butane + oxygen ___________________________________ carbon dioxide + water 2. Write the unbalanced (skeleton) equation. C4H10 + O2 ___________________________________ CO2 + H2O © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 25 ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the combustion of butane (C4H10) gas, where carbon dioxide and water are the only products. 3. Balance the equation. C4H10 + 6.5 O2 C: H: O: 4 10 13 ___________________________________ ___________________________________ 4 CO2 + 5 H2O C: H: O: 4 10 13 ___________________________________ ___________________________________ Atoms balance, but all coefficients must be whole numbers. Multiply equation by 2. 2 C4H10 + 13 O2 © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 26 ___________________________________ 8 CO2 + 10 H2O ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the reaction of magnesium hydroxide and phosphoric acid to form magnesium phosphate and water. a. 3 Mg(OH)2 + 2 H3PO4 b. Mg(OH)2 + H3PO4 ___________________________________ Mg3(PO4)2 + H2O ___________________________________ Mg3(PO4)2 + H2O c. 3 Mg(OH)2 + H3PO4 d. 3 Mg(OH)2 + 2 H3PO4 Mg3(PO4)2 + H2O ___________________________________ Mg3(PO4)2 + 6 H2O 1. Identify the Reaction. ___________________________________ magnesium hydroxide + phosphoric acid magnesium phosphate + water 2. Write the unbalanced (skeleton) equation. Mg3(PO4)2 + H2O Mg(OH)2 + H3PO4 © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 27 ___________________________________ ___________________________________ Balancing Chemical Equations Practice ___________________________________ Write the balanced chemical equation for the reaction of magnesium hydroxide and phosphoric acid to form magnesium phosphate and water. ___________________________________ 3. Balance the equation. 3 Mg(OH)2 + 2 H3PO4 Mg: H: O: PO4: ___________________________________ Mg3(PO4)2 + H2O 3 12 6 2 Mg: H: O: PO4: 3 2 1 2 ___________________________________ ___________________________________ To balance water, add a coefficient of six. 3 Mg(OH)2 + 2 H3PO4 ___________________________________ Mg3(PO4)2 + 6 H2O © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 28 ___________________________________ Information in a Chemical Equation ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 29 ___________________________________ Information from a Chemical Equation ___________________________________ From the chemical equation below, how many moles of HF can be produced from 2 moles of hydrogen gas? H2 (g) + F2 (g) ___________________________________ ___________________________________ 2 HF (g) For every 1 mol of H2, 2 mol of HF can be produced. Two moles of H2 could then produce 4 moles of HF. ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 30 ___________________________________ Information from a Chemical Equation ___________________________________ From the chemical equation below, how many moles of oxygen are needed to burn 2 molecules of propane (C3H8)? C3H8 + 5 O2 ___________________________________ 3 CO2 + 4 H2O a. 5 molecules of oxygen ___________________________________ b. 6 molecules of oxygen c. 10 molecules of oxygen ___________________________________ d. 15 molecules of oxygen ___________________________________ For every 1 molecule of propane, 5 molecules of O2 are needed to fully react. Two molecules of propane would then require 2 x 5 = 10 molecules of oxygen. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 31 ___________________________________ Types of Chemical Equations ___________________________________ Reactions are classified into subtypes to aide in predicting the products of chemical reactions. ___________________________________ Reactions are classified into five major categories: ___________________________________ 1. Combination reactions 2. Decomposition reactions 3. Single displacement reactions 4. Double displacement reactions 5. Oxidation-reduction (redox) reactions (Chapter 17) ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 32 ___________________________________ Combination Reactions ___________________________________ Two reactants combine to give a single product. A+B AB where A or B are elements/compounds and AB is a compound. ___________________________________ Representative Examples ___________________________________ metal + nonmetal 2 Na (s) + Cl2 (g) metal oxide + water CaO (s) + H2O (l) salt ___________________________________ 2 NaCl (s) metal hydroxide ___________________________________ Ca(OH)2 (aq) Violent reaction occurs when Al and Br2 react to form AlBr3. 2 Al (s) + 3 Br2 (l) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 33 ___________________________________ 2 AlBr3 (s) ___________________________________ Decomposition Reactions ___________________________________ A single reactant breaks down (decomposes) into two or more products . ___________________________________ AB A+B Representative Examples 2 PbO2 (s) ∆ ___________________________________ 2 PbO(s) + O2 (g) Metal oxides often decompose when heated. ___________________________________ Carbonates form CO2 when heated. CaCO3 (s) CaO (s) + CO2 (g) ___________________________________ H2O2 decomposes to steam (H2O (g)) and O2. 2 H2O2 (l) ___________________________________ 2 H2O (g) + O2 (g) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 34 ___________________________________ Single Displacement Reactions ___________________________________ One element (A) reacts with a compound (BC) to replace one element in the compound, giving a new element (B) and a different compound (AC). A + BC ___________________________________ B + AC ___________________________________ where A and B are metals and A is more reactive. or A + BC ___________________________________ C + AB where A and C are halogens and A is more reactive. ___________________________________ Example Zn reacts with HCl, resulting in H2 gas evolution. Zn (s) + 2 HCl (aq) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 35 ___________________________________ ZnCl2 (aq) + H2 (g) ___________________________________ Activity Series Table listing in order of decreasing reactivity of various elements. More reactive elements replace less reactive ones. 2 Al (s) + 3 CuCl2 (s) 2 Ag (s) + 3 CuSO4 (s) ___________________________________ ___________________________________ 2 AlCl3 (aq) + 3 Cu (s) ___________________________________ No Reaction ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 36 ___________________________________ General Types of Single Displacement Reactions ___________________________________ Where A and B are metals and A is more reactive: Metal + acid 2 Al (s) + 3 H2SO4 (aq) Metal + water ___________________________________ hydrogen + salt Al2(SO4)3 (aq) + 3 H2 (g) ___________________________________ hydrogen + metal hydroxide/oxide 2 Na (s) + 2 H2O (l) Metal (or halogen) + salt ___________________________________ 2 NaOH (aq) + H2 (g) metal (or halogen) + salt Fe (s) + CuSO4 (aq) Cu (s) + FeSO4 (aq) Cl2 (g) + 2 KI (aq) I2 (s) + 2 KCl (aq) © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ ___________________________________ Slide 37 ___________________________________ Single Displacement Reactions ___________________________________ Will a reaction occur between Ni and HCl? If so, write the balanced chemical equation. ___________________________________ Based on the reactivity series, Ni is more reactive than hydrogen, so a reaction occurs. Ni (s) + HCl (aq) Will a reaction occur between Sn and AlCl3? If so, write the balanced chemical equation. ___________________________________ Based on the reactivity series, Sn is less reactive than Al, so no reaction occurs. ___________________________________ Sn (s) + AlCl3 (aq) No Reaction © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 38 ___________________________________ H2 (g) + NiCl2 (aq) ___________________________________ ___________________________________ Single Displacement Reactions ___________________________________ Write the reaction (if it occurs) between the following substances: Iron metal and a solution of magnesium chloride ___________________________________ ___________________________________ a. Fe (s) + MgCl2 (aq) No Reaction b. Fe (s) + MgCl2 (aq) FeCl2 (aq) + Mg (s) ___________________________________ ___________________________________ Iron is less reactive than Mg, so no reaction occurs. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 39 ___________________________________ ___________________________________ Double Displacement Reactions ___________________________________ Two compounds exchange partners with one another to yield two new compounds. AB + CD ___________________________________ AD + CB Physical evidence for a double displacement reaction include: heat evolution, formation of a precipitate or gas production. ___________________________________ ___________________________________ ___________________________________ PbI2 precipitates from the reaction of Pb(NO3)2 with KI. Pb(NO3)2 (aq) + 2 KI (aq) ___________________________________ PbI2 (s) + 2KNO3 (aq) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 40 ___________________________________ General Types of Double Displacement Reactions ___________________________________ Acid/Base Neutralization acid + base ___________________________________ salt + water + heat HCl (aq) + NaOH (aq) ___________________________________ NaCl (aq) + H2O (l) + heat ___________________________________ Metal Oxide (base) + Acid Metal oxide + acid CuO (s) + 2 HNO3 (aq) Cu(NO3)2 (aq) + H2O (l) + heat © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 41 ___________________________________ salt + water + heat ___________________________________ ___________________________________ General Types of Double Displacement Reactions ___________________________________ Formation of a Precipitate Product solubilities are based on the table in Appendix V ___________________________________ Insoluble products are indicated by (s) BaCl2 (aq) + 2 AgNO3 (aq) ___________________________________ 2 AgCl (s) + 2 KNO3 (aq) Gas Formation H2SO4 (l) + NaCl (s) ___________________________________ NaHSO4 (aq) + HCl (g) A gas can also form from a secondary reaction after displacement 2 HCl (aq) + Na2CO3 (aq) H2CO3 (aq) 2 NaCl (aq) + H2CO3 (aq) 42 ___________________________________ H2O (l) + CO2 (g) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ ___________________________________ Writing Reaction Equations Practice ___________________________________ Write the reaction equation between aqueous solution of hydroiodic acid and sodium hydroxide. ___________________________________ First convert names to chemical formulas and determine the type of reaction. ___________________________________ HI (acid)/NaOH(base) ___________________________________ Neutralization Reaction acid + base HI (aq) + NaOH (aq) salt + water ___________________________________ NaI (aq) + H2O (l) ___________________________________ Salt formula must charge balance (Na+ and I–) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 43 ___________________________________ Writing Reaction Equations Practice ___________________________________ Write the balanced reaction equation between aqueous barium chloride and magnesium sulfate. ___________________________________ First convert names to chemical formulas and determine the type of reaction. ___________________________________ BaCl2/MgSO4 Both compounds are ionic, but not acids or bases. ___________________________________ The reaction is likely a double displacement. BaCl2 (aq) + MgSO4 (aq) BaSO4 (s) + MgCl2 (aq) ___________________________________ Based on Appendix V, BaSO4 will precipitate, providing a driving force for the reaction. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 44 ___________________________________ ___________________________________ Writing Reaction Equations Practice ___________________________________ Write the balanced reaction equation between aqueous potassium phosphate and barium chloride. 1. Convert names to formulas ___________________________________ K3PO4/BaCl2 Both compounds are ionic, but not acids or bases. ___________________________________ The reaction is likely a double displacement. Based on Appendix V, Ba3(PO4)2 will precipitate, providing a driving force for the reaction a. K3PO4 (aq) + BaCl2 (aq) No Reaction b. K3PO4 (aq) + BaCl2 (aq) KCl (aq) + Ba3(PO4)2 (aq) c. 2 K3PO4 (aq) + 3 BaCl2 (aq) d. 2 K3PO4 (aq) + 3 BaCl2 (aq) 45 ___________________________________ 6 KCl (aq) + Ba3(PO4)2 (s) ___________________________________ 6 KCl (s) + Ba3(PO4)2 (aq) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ ___________________________________ Writing Reaction Equations Practice ___________________________________ Write the balanced reaction equation between aqueous ammonium chloride and sodium nitrate. 1. Convert names to formulas NH4Cl/NaNO3 Both compounds are ionic. ___________________________________ ___________________________________ The reaction is likely a double displacement. Based on Appendix V, neither compound will precipitate. a. NH4Cl (aq) + NaNO3 (aq) ___________________________________ No Reaction b. NH4Cl (aq) + NaNO3 (aq) NH4NO3 (aq) + NaCl (aq) c. NH4Cl (aq) + NaNO3 (aq) NH4NO3(s) + NaCl (aq) d. NH4Cl (aq) + NaNO3 (aq) NH4NO3 (aq) + NaCl (s) © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ ___________________________________ Slide 46 ___________________________________ Heat in Chemical Reactions Terminology Energy transfer and changes accompany any chemical reaction. ___________________________________ Heat of reaction: quantity of heat actually produced during a chemical reaction. ___________________________________ Units: kilojoules (kJ) or kilocalories (kcal) ___________________________________ Exothermic reactions: release heat H2 (g) + Cl2 (g) ___________________________________ 2 HCl (g) + 185 kJ Heat can be treated as a product ___________________________________ Endothermic reactions: absorb heat N2 (g) + O2 (g) + 181 kJ 2 NO (g) ___________________________________ Heat can be treated as a reactant © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 47 ___________________________________ Heat in Chemical Reactions Terminology ___________________________________ Energy transfer and changes accompany any chemical reaction. ___________________________________ Heat of reaction: quantity of heat actually produced during a chemical reaction. ___________________________________ Units: kilojoules (kJ) or kilocalories (kcal) ___________________________________ C (s) + O2 (g) CO2 (g) + 393 kJ ___________________________________ 1 mol of C reacts with 1 mol of O2 to provide 1 mol of CO2 and 393 kJ of heat are released. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 48 ___________________________________ ___________________________________ Heat in Chemical Reactions Practice ___________________________________ In the reaction: H2 (g) + I2 (s) + 12.6 kJ 2 HI (g) ___________________________________ When 4 moles of HI are produced: ___________________________________ a. 12.6 kJ of energy is absorbed b. 25.2 kJ of energy is absorbed ___________________________________ c. 12.6 kJ of energy is released d. 25.2 kJ of energy is released ___________________________________ 12.6 kJ are absorbed to form 2 mol of HI. 2 x 12.6 kJ are needed to produce 4 mol of HI. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 49 Heat as an Energy Transfer Vehicle in Nature ___________________________________ Photosynthesis: converts energy in the form of light from the sun into chemical energy (bonds in glucose). ___________________________________ 6 CO2 (g) + 6 H2O (l) + 2519 kJ ___________________________________ ___________________________________ C6H12O6 + 6 O2 (g) glucose ___________________________________ Photosynthesis is endothermic: the needed energy is supplied by sunlight. ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 50 ___________________________________ Heat as an Energy Transfer Vehicle in Nature ___________________________________ Fossil Fuels: petroleum, coal, and natural gas all release significant amounts of energy during combustion. CH4 (g) + 2 O2 (g) ___________________________________ ___________________________________ CO2 (g) + 2 H2O (g) + 890 kJ ___________________________________ Combustion does not occur at normal temperatures without a spark. ___________________________________ Activation energy: Amount of energy needed to initiate a chemical reaction. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 51 ___________________________________ ___________________________________ Graphical Representations of Endothermic Reactions ___________________________________ Reaction Coordinate Diagram ___________________________________ ___________________________________ ___________________________________ ___________________________________ Products are at a higher potential energy than reactants. Activation energy: Amount of energy needed to initiate a chemical reaction. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 52 ___________________________________ Graphical Representations of Exothermic Reactions ___________________________________ Reaction Coordinate Diagram ___________________________________ ___________________________________ ___________________________________ ___________________________________ Products are at a lower potential energy than reactants. Activation energy: Amount of energy needed to initiate a chemical reaction. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 53 ___________________________________ ___________________________________ Global Warming: The Greenhouse Effect ___________________________________ Fossil fuels produce CO2 during combustion. 50 billion tons of CO2 are released into the atmosphere annually. ___________________________________ Concentration of CO2 in the atmosphere. ___________________________________ ___________________________________ ___________________________________ The average global temperature has risen by 0.74 ºC over the past century. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 54 ___________________________________ ___________________________________ Global Warming: The Greenhouse Effect ___________________________________ Other greenhouse gases also affect the atmosphere. ___________________________________ Methane (CH4) is a very potent greenhouse gas. ___________________________________ Levels of methane have increased over the past century due to coal mining, agricultural development and cows! ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 55 ___________________________________ Global Warming: The Greenhouse Effect How do greenhouse gases warm the atmosphere? ___________________________________ Greenhouse gases trap heat near Earth’s surface. 1. Solar radiation warms the Earth’s surface. 2. Greenhouse gases absorb some of this heat, which warms the atmosphere. ___________________________________ ___________________________________ ___________________________________ Greenhouses operate in a similar fashion, allowing sunlight in but not the outflow of heat produced. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 56 ___________________________________ ___________________________________ ___________________________________ Learning Objectives ___________________________________ 8.1 The Chemical Equation Describe the information present in a chemical equation. ___________________________________ 8.2 Writing and Balancing Chemical Equations ___________________________________ Write and balance chemical equations. ___________________________________ 8.3 Types of Chemical Equations ___________________________________ Give examples of the following types of reactions: combination, decomposition, single displacement and double displacement. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 57 ___________________________________ ___________________________________ Learning Objectives ___________________________________ 8.4 Heat in Chemical Reactions ___________________________________ Explain the following terms as they relate to a chemical reaction: exothermic, endothermic, heat of a reaction and activation energy. 8.5 Global Warming: The Greenhouse Effect ___________________________________ Recognize CO2 levels are increasing and the effect greenhouse gases have on warming the atmosphere near the Earth’s surface. ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ ___________________________________