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Exo- and Endothermic Reactions

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Exo- and Endothermic Reactions Exothermic reaction: A chemical reaction that results in the net production of energy. reactants products + energy – PowerPoint PPT presentation

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Title: Exo- and Endothermic Reactions


1
Exo- and Endothermic Reactions
Exothermic reaction A chemical reaction that
results in the net production of energy.
reactants products
energy
2
In total, how many atoms are represented by the
following schematic for a chemical reaction?
Chemical Reactions and Equations CHECK YOUR
ANSWER
  • A. 2
  • 5
  • 6
  • 12

products
Explanation The atoms of the reactants are the
SAME atoms of the products, except in a different
configuration.
3
Exo- and Endothermic Reactions
  • Exothermic reaction A chemical reaction that
    results in the net production of energy.
  • reactants products
    energy

4
Exo- and Endothermic Reactions
  • 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

5
Exo- and Endothermic Reactions
6
Use the bond energies below to determine whether
the following reaction is exothermic or
endothermic
Exo- and Endothermic Reactions CHECK YOUR
NEIGHBOR
H-H (bond energy 436 kJ/mol) Cl-Cl (bond energy
243 kJ/mol) H-Cl (bond energy 431 kJ/mol)
H2 Cl2 ? 2 HCl
  • Exothermic with more than 50 kJ of energy
    released.
  • Endothermic with more than 50 kJ of energy
    absorbed.
  • Endothermic with less than 50 kJ of energy
    absorbed.
  • Exothermic with less than 50 kJ of energy
    released.

7
Use the bond energies below to determine whether
the following reaction is exothermic or
endothermic
Exo- and Endothermic Reactions CHECK YOUR ANSWER
H-H (bond energy 436 kJ/mol) Cl-Cl (bond energy
243 kJ/mol) H-Cl (bond energy 431 kJ/mol)
H2 Cl2 ? 2 HCl
  • Exothermic with more than 50 kJ of energy
    released.
  • Endothermic with more than 50 kJ of energy
    absorbed.
  • Endothermic with less than 50 kJ of energy
    absorbed.
  • Exothermic with less than 50 kJ of energy
    released.

8
Use the bond energies below to determine whether
the following reaction is exothermic or
endothermic
Exo- and Endothermic Reactions CHECK YOUR ANSWER
H-H (bond energy 436 kJ/mol) Cl-Cl (bond energy
243 kJ/mol) H-Cl (bond energy 431 kJ/mol)
H2 Cl2 ? 2 HCl
431 kJ/mol
436 kJ/mol
243 kJ/mol
431 kJ/mol
  • Exothermic with more than 50 kJ of energy
    released.
  • Endothermic with more than 50 kJ of energy
    absorbed.
  • Endothermic with less than 50 kJ of energy
    absorbed.
  • Exothermic with less than 50 kJ of energy
    released.

9
Use the bond energies below to determine whether
the following reaction is exothermic or
endothermic
Exo- and Endothermic Reactions CHECK YOUR ANSWER
H-H (bond energy 436 kJ/mol) Cl-Cl (bond energy
243 kJ/mol) H-Cl (bond energy 431 kJ/mol)
H2 Cl2 ? 2 HCl
431 kJ/mol
436 kJ/mol
243 kJ/mol
431 kJ/mol
  • Exothermic with more than 50 kJ of energy
    released.
  • Endothermic with more than 50 kJ of energy
    absorbed.
  • Endothermic with less than 50 kJ of energy
    absorbed.
  • Exothermic with less than 50 kJ of energy
    released.

10
Use the bond energies below to determine whether
the following reaction is exothermic or
endothermic
Exo- and Endothermic Reactions CHECK YOUR ANSWER
H-H (bond energy 436 kJ/mol) Cl-Cl (bond energy
243 kJ/mol) H-Cl (bond energy 431 kJ/mol)
H2 Cl2 ? 2 HCl
431 kJ/mol
436 kJ/mol
243 kJ/mol
431 kJ/mol
679 kJ/mol (absorbed)
862 kJ/mol (released)
  • Exothermic with more than 50 kJ of energy
    released.
  • Endothermic with more than 50 kJ of energy
    absorbed.
  • Endothermic with less than 50 kJ of energy
    absorbed.
  • Exothermic with less than 50 kJ of energy
    released.

11
Use the bond energies below to determine whether
the following reaction is exothermic or
endothermic
Exo- and Endothermic Reactions CHECK YOUR ANSWER
H-H (bond energy 436 kJ/mol) Cl-Cl (bond energy
243 kJ/mol) H-Cl (bond energy 431 kJ/mol)
H2 Cl2 ? 2 HCl
431 kJ/mol
436 kJ/mol
243 kJ/mol
431 kJ/mol
D 862 679 183 kJ/mol released
679 kJ/mol (absorbed)
862 kJ/mol (released)
  • Exothermic with more than 50 kJ of energy
    released.
  • Endothermic with more than 50 kJ of energy
    absorbed.
  • Endothermic with less than 50 kJ of energy
    absorbed.
  • Exothermic with less than 50 kJ of energy
    released.

12
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
13
Which type of chemical reaction leads to a
greater dispersal of energy?
Entropy and Chemical Reactions CHECK YOUR ANSWER
Exothermic
Endothermic
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