Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hewitt/Lyons/Suchocki/Yeh Conceptual Integrated Science Chapter 13 CHEMICAL.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley This lecture will help you understand: Chemical Reactions and Equations Acid–Base Reactions Salts Solutions: Acidic, Basic, or Neutral The pH Scale Oxidation-Reduction Reactions Corrosion and Combustion Reaction Rates Exo- and Endothermic Reactions Entropy and Chemical Reactions

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Chemical Reactions and Equations During a chemical reaction, one or more new compounds are formed as a result of the rearrangement of atoms. Reactants Products

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Chemical Reactions and Equations Law of Mass Conservation: No atoms are gained or lost during any reaction. The number of times atoms appear before the arrow must be equal to the number of times they appear after the arrow.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley In total, how many atoms are represented by the following schematic for a chemical reaction? A.2 B.5 C.6 D.12 Chemical Reactions and Equations CHECK YOUR NEIGHBOR

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley In total, how many atoms are represented by the following schematic for a chemical reaction? A.2 B.5 C.6 D.12 Chemical Reactions and Equations CHECK YOUR ANSWER Explanation: The atoms of the reactants are the SAME atoms of the products, except in a different configuration.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley In total, how many atoms are represented by the following schematic for a chemical reaction? A.2 B.5 C.6 D.12 Chemical Reactions and Equations CHECK YOUR ANSWER Explanation: The atoms of the reactants are the SAME atoms of the products, except in a different configuration. reactants

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley In total, how many atoms are represented by the following schematic for a chemical reaction? A.2 B.5 C.6 D.12 Chemical Reactions and Equations CHECK YOUR ANSWER Explanation: The atoms of the reactants are the SAME atoms of the products, except in a different configuration. products

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley In total, how many atoms are represented by the following schematic for a chemical reaction? A.2 B.5 C.6 D.12 Chemical Reactions and Equations CHECK YOUR ANSWER products “conventional” equation format All you see here are six different atoms!

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley How many “diatomic” molecules are represented? A.1 B.2 C.3 D.4 Chemical Reactions and Equations CHECK YOUR ANSWER Explanation: The diatomic molecule shown with the products is actually the same molecule shown to the left with the reactants. What happened here is that this molecule didn’t react. beforeafter

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Is the following chemical equation balanced? A.No, because the molecules have changed. B.Yes, because the coefficients on each side add up to the same number. C.No, because there are more oxygen atoms in the products. D.Yes, because the same atoms appear before and after. Chemical Reactions and Equations CHECK YOUR NEIGHBOR 1 CH 4 + 2 O 2  2 H 2 O + 1 CO 2

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Is the following chemical equation balanced? A.No, because the molecules have changed. B.Yes, because the coefficients on each side add up to the same number. C.No, because there are more oxygen atoms in the products. D.Yes, because the same atoms appear before and after. Chemical Reactions and Equations CHECK YOUR ANSWER 1 CH 4 + 2 O 2  2 H 2 O + 1 CO 2

H2OH2OHCl +

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley When water behaves as an acid, what does it lose? A.A hydrogen ion. B.A hydrogen atom. C.An electron. D.Water can’t behave as an acid. Acid–Base Reactions CHECK YOUR NEIGHBOR

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley When water behaves as an acid, what does it lose? A.A hydrogen ion. B.A hydrogen atom. C.An electron. D.Water can’t behave as an acid. Acid – Base Reactions CHECK YOUR ANSWER

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley When water behaves as a base, what does it gain? A.A hydrogen ion. B.A hydrogen atom. C.An electron. D.Water can’t behave as an acid. Acid – Base Reactions CHECK YOUR NEIGHBOR

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley When water behaves as a base, what does it gain? A.A hydrogen ion. B.A hydrogen atom. C.An electron. D.Water can’t behave as an acid. Acid – Base Reactions CHECK YOUR ANSWER

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Which water molecule is behaving as an acid, and which is behaving as a base? A.Molecule B as a base; Molecule A as an acid B.Molecule B as an acid; Molecule A as a base C.Both Molecules A and B are behaving as acids. D.Both Molecules A and B are behaving as bases. Acid – Base Reactions CHECK YOUR NEIGHBOR Molecule AMolecule B H O H H + H O H H O H O H –

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Which water molecule is behaving as an acid, and which is behaving as a base? A.Molecule B as a base; Molecule A as an acid B.Molecule B as an acid; Molecule A as a base C.Both Molecules A and B are behaving as acids. D.Both Molecules A and B are behaving as bases. Acid – Base Reactions CHECK YOUR ANSWER Molecule AMolecule B H O H H + H O H H O H O H –

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Which water molecule is behaving as an acid, and which is behaving as a base? A.Molecule B as a base; Molecule A as an acid B.Molecule B as an acid; Molecule A as a base C.Both Molecules A and B are behaving as acids. D.Both Molecules A and B are behaving as bases. Acid – Base Reactions CHECK YOUR ANSWER Molecule AMolecule B H O H H O H

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Which water molecule is behaving as an acid, and which is behaving as a base? A.Molecule B as a base; Molecule A as an acid B.Molecule B as an acid; Molecule A as a base C.Both Molecules A and B are behaving as acids. D.Both Molecules A and B are behaving as bases. Acid – Base Reactions CHECK YOUR ANSWER Molecule A H O H H+H+ O H –

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Which water molecule is behaving as an acid, and which is behaving as a base? A.Molecule B as a base; Molecule A as an acid B.Molecule B as an acid; Molecule A as a base C.Both Molecules A and B are behaving as acids. D.Both Molecules A and B are behaving as bases. Acid – Base Reactions CHECK YOUR ANSWER + H O H H O H –

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley What salt forms from the reaction of hydrogen chloride, HCl, with potassium hydroxide, KOH? A.KCl B.H 3 OCl C.KOH 2 D.KOH 2 Cl Salts CHECK YOUR NEIGHBOR

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley What salt forms from the reaction of hydrogen chloride, HCl, with potassium hydroxide, KOH? A.KCl B.H 3 OCl C.KOH 2 D.KOH 2 Cl Salts CHECK YOUR ANSWER Explanation: The K + from the KOH combines with the Cl – from the HCl.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Solutions: Acidic, Basic, or Neutral Water can behave as an acid or a base. In pure water, for every one hydronium ion, H 3 O +, formed, there is a hydroxide ion, OH –, formed.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Solutions: Acidic, Basic, or Neutral Water can behave as an acid or a base. In pure water, for every one hydronium ion, H 3 O +, formed, there is a hydroxide ion, OH –, formed. So in pure water, [H 3 O + ] = [OH – ] = 0.0000001 M = 10 –7 M.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Solutions: Acidic, Basic, or Neutral Water can behave as an acid or a base. In pure water, for every one hydronium ion, H 3 O +, formed, there is a hydroxide ion, OH –, formed. So, in pure water, [H 3 O + ] = [OH – ] = 0.0000001 M = 10 –7 M.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Solutions: Acidic, Basic, or Neutral Water can behave as an acid or a base. Add hydronium ions, H 3 O +, and the solution is “acidic,” Add hydroxide ions, OH –, and the solution is “basic.”

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley As sodium hydroxide, NaOH, is added to water, the hydroxide ion, OH –, concentration A.increases. B.decreases. C.remains the same. Solutions: Acidic, Basic, or Neutral CHECK YOUR NEIGHBOR

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley As sodium hydroxide, NaOH, is added to water, the hydroxide ion, OH –, concentration A.increases. B.decreases. C.remains the same. Solutions: Acidic, Basic, or Neutral CHECK YOUR ANSWER Explanation: The bond between sodium and oxygen is ionic. When dissolved in water, it separates into sodium ions and hydroxide ions, much like sodium chloride, NaCl, separates into sodium and chloride ions.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale pH is a measure of the concentration of hydronium ions, H 3 O +. pH = –log [H 3 O + ] For pure water: pH = –log (10 –7 ) pH = –(– 7) pH = 7

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale pH is a measure of the concentration of hydronium ions, H 3 O +. pH = –log [H 3 O + ] For pure water: pH = –log (10 –7 ) pH = –(–7) pH = 7 What is a log?

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. Quiz Time What is the log of 10 2 ?

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. Quiz Time What is the log of 10 2 ? Log 10 2 = 2 (the power to which 10 is raised)

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 –1 = 0.1

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 –1 = 0.1 10 –2 = 0.01

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = ? 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Three zeros

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = ? 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Two zeros

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = ? 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 One zero

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Zero zeros!

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Quiz Time Log 1000 = ?

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Quiz Time Log 1000 = ? Log 10 3 =

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Quiz Time Log 1000 = ? Log 10 3 = 3

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Quiz Time Log 1 = ?

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Quiz Time Log 1 = ? Log 10 0 =

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Quiz Time Log 1 = ? Log 10 0 = 0

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Quiz Time Log 10 – 7 =

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley The pH Scale The “log” of a number is simply the power to which ten is raised. The log of 10 3, for example, is 3. 10 3 = 1000 10 2 = 100 10 1 = 10 10 0 = 1 10 –1 = 0.1 10 –2 = 0.01 10 –3 = 0.001 Quiz Time Log 10 – 7 = – 7

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Oxidation-Reduction Reactions Oxidation: The loss of an electron 2 Na 2 Na + + 2 e – Reduction: The gain of an electron Cl 2 + 2 e – 2 Cl –

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Oxidation-Reduction Reactions Oxidation: The loss of an electron 2 Na 2 Na + + 2 e – Reduction: The gain of an electron Cl 2 + 2 e – 2 Cl – “Leo” “Ger”

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Oxidation-Reduction Reactions Oxidation: The loss of an electron 2 Na 2 Na + + 2 e – Reduction: The gain of an electron Cl 2 + 2 e – 2 Cl – “Leo” “Ger” (Leo the lion went “Ger”)

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley What element within the reactants is oxidized in the following equation, and what element is reduced? I 2 + 2 Br –  2 I – + Br 2 A.Iodine, I, is oxidized, while the bromine ion, Br –, is reduced. B.Iodine, I, is reduced, while the bromine ion, Br –, is oxidized. C.Both the iodine, I, and the bromine ion, Br –, are reduced. D.Both the iodine, I, and the bromine ion, Br –, are oxidized. Oxidation Reduction Reactions CHECK YOUR NEIGHBOR

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley I 2 + 2 Br –  2 I – + Br 2 A.Iodine, I, is oxidized, while the bromine ion, Br –, is reduced. B.Iodine, I, is reduced, while the bromine ion, Br –, is oxidized. C.Both the iodine, I, and the bromine ion, Br –, are reduced. D.Both the iodine, I, and the bromine ion, Br –, are oxidized. Explanation: Note how the iodine gains a negative charge, while the bromine loses the negative charge. What element within the reactants is oxidized in the following equation and what element is reduced? Oxidation Reduction Reactions CHECK YOUR ANSWER

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Corrosion and Combustion Corrosion The process whereby a metal deteriorates through oxidation-reduction reactions. It can be prevented by coating the metal with zinc, which oxidizes first.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Corrosion and Combustion Combustion An oxidation-reduction reaction between a nonmetallic material, such as wood, and oxygen.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley One of the products of combustion is water. Why doesn’t this water extinguish the combustion? A.While areas of combustion are being extinguished, new areas are combusting. B.Combustion only produces micro amounts of water. C.The chemical combustion reaction is happening too fast for the water to have an effect on the fire. D.This water is in the gaseous phase and merely floats away. Corrosion and Combustion CHECK YOUR NEIGHBOR

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley One of the products of combustion is water. Why doesn’t this water extinguish the combustion? A.While areas of combustion are being extinguished, new areas are combusting. B.Combustion only produces micro amounts of water. C.The chemical combustion reaction is happening too fast for the water to have an effect on the fire. D.This water is in the gaseous phase and merely floats away. Corrosion and Combustion CHECK YOUR ANSWER Explanation: Carefully place your hand over a campfire, and you can feel the greater humidity as water vapor escapes.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Reaction Rates Reaction rate: The speed with which products form from the reactants. Affected by Concentration Temperature Catalyst

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Reaction Rates Reaction rate: The speed with which products form from the reactants. Affected by Concentration Temperature Catalyst Premise: Reactant molecules have to make physical contact with each other in order to transform into products.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Reaction Rates Reaction rate: The speed with which products form from the reactants. Affected by Concentration The more concentrated a sample of nitrogen and oxygen, the greater the likelihood that N 2 and O 2 molecules will collide and form nitrogen monoxide.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Reaction Rates Reaction rate: The speed with which products form from the reactants. Affected by Temperature Slow-moving molecules may collide without enough force to break the bonds. In this case, they cannot react to form product molecules.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Reaction Rates Reaction rate: The speed with which products form from the reactants. Affected by Catalysts Reactant molecules must gain a minimum amount of energy, called the activation energy, E act, in order to transform into product molecules.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Reaction Rates Reaction rate: The speed with which products form from the reactants. Affected by Catalysts A catalyst has the effect of lowering the activation energy, which allows for the reaction to proceed at a quicker rate.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Carefully examine the following reaction sequence for the catalytic formation of ozone, O 3, from molecular oxygen, O 2. Which chemical compound is behaving as the catalyst? A. Nitrogen dioxide, NO 2 B.Nitrogen monoxide, NO C.Atomic oxygen, O D.Oxygen, O 2 Reaction Rates CHECK YOUR NEIGHBOR O 2 + 2 NO  2 NO 2 2 NO 2  2 NO + 2 O 2 O + 2 O 2  2 O 3

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley O 2 + 2 NO  2 NO 2 2 NO 2  2 NO + 2 O 2 O + 2 O 2  2 O 3 Carefully examine the following reaction sequence for the catalytic formation of ozone, O 3, from molecular oxygen, O 2. Which chemical compound is behaving as the catalyst? A. Nitrogen dioxide, NO 2 B.Nitrogen monoxide, NO C.Atomic oxygen, O D.Oxygen, O 2 Reaction Rates CHECK YOUR ANSWER Explanation: The NO reacts with O 2 to form O, which reacts with O 2 to form O 3. In other words, the NO gets this reaction going. As another clue, note how NO is regenerated after the second reaction.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Exo- and Endothermic Reactions Exothermic reaction: A chemical reaction that results in the net production of energy. reactants products + energy

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Exothermic reaction: A chemical reaction that results in the net production of energy. reactants products + energy Endothermic reaction: A chemical reaction in which there is a net consumption of energy. energy + reactants products Exo- and Endothermic Reactions

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Use the bond energies below to determine whether the following reaction is exothermic or endothermic: Exo- and Endothermic Reactions CHECK YOUR NEIGHBOR A. Exothermic with more than 50 kJ of energy released. B. Endothermic with more than 50 kJ of energy absorbed. C. Endothermic with less than 50 kJ of energy absorbed. D. Exothermic with less than 50 kJ of energy released. H 2 + Cl 2  2 HCl H-H(bond energy: 436 kJ/mol) Cl-Cl(bond energy: 243 kJ/mol) H-Cl(bond energy: 431 kJ/mol)

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Use the bond energies below to determine whether the following reaction is exothermic or endothermic: Exo- and Endothermic Reactions CHECK YOUR ANSWER A. Exothermic with more than 50 kJ of energy released. B. Endothermic with more than 50 kJ of energy absorbed. C. Endothermic with less than 50 kJ of energy absorbed. D. Exothermic with less than 50 kJ of energy released. H 2 + Cl 2  2 HCl H-H(bond energy: 436 kJ/mol) Cl-Cl(bond energy: 243 kJ/mol) H-Cl(bond energy: 431 kJ/mol)

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Use the bond energies below to determine whether the following reaction is exothermic or endothermic: Exo- and Endothermic Reactions CHECK YOUR ANSWER A. Exothermic with more than 50 kJ of energy released. B. Endothermic with more than 50 kJ of energy absorbed. C. Endothermic with less than 50 kJ of energy absorbed. D. Exothermic with less than 50 kJ of energy released. H 2 + Cl 2  2 HCl H-H(bond energy: 436 kJ/mol) Cl-Cl(bond energy: 243 kJ/mol) H-Cl(bond energy: 431 kJ/mol) 436 kJ/mol243 kJ/mol 431 kJ/mol

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Use the bond energies below to determine whether the following reaction is exothermic or endothermic: Exo- and Endothermic Reactions CHECK YOUR ANSWER A. Exothermic with more than 50 kJ of energy released. B. Endothermic with more than 50 kJ of energy absorbed. C. Endothermic with less than 50 kJ of energy absorbed. D. Exothermic with less than 50 kJ of energy released. H 2 + Cl 2  2 HCl H-H(bond energy: 436 kJ/mol) Cl-Cl(bond energy: 243 kJ/mol) H-Cl(bond energy: 431 kJ/mol) 436 kJ/mol243 kJ/mol 431 kJ/mol 679 kJ/mol (absorbed) 862 kJ/mol (released)

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Use the bond energies below to determine whether the following reaction is exothermic or endothermic: Exo- and Endothermic Reactions CHECK YOUR ANSWER A. Exothermic with more than 50 kJ of energy released. B. Endothermic with more than 50 kJ of energy absorbed. C. Endothermic with less than 50 kJ of energy absorbed. D. Exothermic with less than 50 kJ of energy released. H 2 + Cl 2  2 HCl H-H(bond energy: 436 kJ/mol) Cl-Cl(bond energy: 243 kJ/mol) H-Cl(bond energy: 431 kJ/mol) 436 kJ/mol243 kJ/mol 431 kJ/mol 679 kJ/mol (absorbed) 862 kJ/mol (released)  = 862 – 679 = 183 kJ/mol released

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions It is the natural tendency of energy to disperse from where it is concentrated to where it is dilute.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions It is the natural tendency of energy to disperse from where it is concentrated to where it is dilute. Examples A hot pan radiates heat

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions It is the natural tendency of energy to disperse from where it is concentrated to where it is dilute. Examples A hot pan radiates heat Gasoline combusts into smaller molecules

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions It is the natural tendency of energy to disperse from where it is concentrated to where it is dilute. Examples A hot pan radiates heat Gasoline combusts into smaller molecules Marbles bouncing on the floor come to a stop

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions It is the natural tendency of energy to disperse from where it is concentrated to where it is dilute. Entropy: The term used to describe the degree to which energy has become dispersed.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions It is the natural tendency of energy to disperse from where it is concentrated to where it is dilute. Entropy: The term used to describe the degree to which energy has become dispersed. Reactions that result in an increase in entropy (energy dispersal) tend to occur on their own.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Which type of chemical reaction leads to a greater dispersal of energy? Entropy and Chemical Reactions CHECK YOUR NEIGHBOR ExothermicEndothermic

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Which type of chemical reaction leads to a greater dispersal of energy? Entropy and Chemical Reactions CHECK YOUR ANSWER ExothermicEndothermic

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions Exothermic reactions tend to be self-sustaining, because they lead to large increases in entropy.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions Exothermic reactions tend to be self-sustaining because they lead to large increases in entropy. Example: A campfire

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions Exothermic reactions tend to be self-sustaining because they lead to large increases in entropy. Endothermic reactions tend to require the continual input of energy. Example: A campfire

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Entropy and Chemical Reactions Exothermic reactions tend to be self-sustaining because they lead to large increases in entropy. Endothermic reactions tend to require the continual input of energy. Example: A campfire Example: Photosynthesis

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hewitt/Lyons/Suchocki/Yeh Conceptual Integrated Science Chapter 13 CHEMICAL.

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hewitt/Lyons/Suchocki/Yeh Conceptual Integrated Science Chapter 13 CHEMICAL.

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