Title: Exo- and Endothermic Reactions
1Exo- and Endothermic Reactions
Exothermic reaction A chemical reaction that
results in the net production of energy.
reactants products
energy
2In total, how many atoms are represented by the
following schematic for a chemical reaction?
Chemical Reactions and Equations CHECK YOUR
ANSWER
products
Explanation The atoms of the reactants are the
SAME atoms of the products, except in a different
configuration.
3Exo- and Endothermic Reactions
- Exothermic reaction A chemical reaction that
results in the net production of energy. - reactants products
energy -
-
4Exo- 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 -
5Exo- and Endothermic Reactions
6Use 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.
7Use 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.
8Use 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.
9Use 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.
10Use 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.
11Use 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.
12Entropy 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
13Which type of chemical reaction leads to a
greater dispersal of energy?
Entropy and Chemical Reactions CHECK YOUR ANSWER
Exothermic
Endothermic