Chemical Reactions

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Chemical Reactions

• Preview
• Understanding Concepts
• Reading Skills
• Interpreting Graphics

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Understanding Concepts

• 1. What type of reaction is Pb(NO3)2 2KI ? PbI2
  2KNO3?
• A. a synthesis reaction
• B. a combustion reaction
• C. a decomposition reaction
• D. a double-displacement reaction

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Understanding Concepts, continued

• 1. What type of reaction is Pb(NO3)2 2KI ? PbI2
  2KNO3?
• A. a synthesis reaction
• B. a combustion reaction
• C. a decomposition reaction
• D. a double-displacement reaction

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Understanding Concepts, continued

• 2. Which of the following describes an
  endothermic chemical reaction?
• F. the explosion of fireworks in the sky
• G. photosynthesis in plant cells
• H. respiration in animal cells
• I. the burning of wood in a fireplace

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Understanding Concepts, continued

• 2. Which of the following describes an
  endothermic chemical reaction?
• F. the explosion of fireworks in the sky
• G. photosynthesis in plant cells
• H. respiration in animal cells
• I. the burning of wood in a fireplace

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Understanding Concepts, continued

• 3. Which of the following changes will always
  increase the rate of a chemical reaction?
• A. lowering the temperature
• B. adding an inhibitor to the reaction mixture
• C. increasing the concentration of the reactants
• D. decreasing the surface area of the reactants

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Understanding Concepts, continued

• 3. Which of the following changes will always
  increase the rate of a chemical reaction?
• A. lowering the temperature
• B. adding an inhibitor to the reaction mixture
• C. increasing the concentration of the reactants
• D. decreasing the surface area of the reactants

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Understanding Concepts, continued

• 4. The equation PCl3 Cl2 ? PCl5 energy
  describes an equilibrium system. How would
  raising the temperature affect the system?
• F. The equilibrium would move to the right to
  create more PCl3 and Cl2.
• G. The equilibrium would move to the left to
  create more PCl3 and Cl2.
• H. The equilibrium would move to the right to
  create more PCl5.
• I. The equilibrium would move to the left to
  create more PCl5.

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Understanding Concepts, continued

• 4. The equation PCl3 Cl2 ? PCl5 energy
  describes an equilibrium system. How would
  raising the temperature affect the system?
• F. The equilibrium would move to the right to
  create more PCl3 and Cl2.
• G. The equilibrium would move to the left to
  create more PCl3 and Cl2.
• H. The equilibrium would move to the right to
  create more PCl5.
• I. The equilibrium would move to the left to
  create more PCl5.

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Understanding Concepts, continued

• 4. The equation PCl3 Cl2 ? PCl5 energy
  describes an equilibrium system. How would
  raising the temperature affect the system?
• F. The equilibrium would move to the right to
  create more PCl3 and Cl2.
• G. The equilibrium would move to the left to
  create more PCl3 and Cl2.
• H. The equilibrium would move to the right to
  create more PCl5.
• I. The equilibrium would move to the left to
  create more PCl5.

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Understanding Concepts, continued

• 5. In the redox reaction H2 F2 ? 2HF, which
  element is reduced, and which is oxidized?

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Understanding Concepts, continued

• 5. In the redox reaction H2 F2 ? 2HF, which
  element is reduced, and which is oxidized?
• Answer F is reduced and H is oxidized.

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Reading Skills

• NITROGEN FIXATION
• The element nitrogen makes up about 78 of
  Earths atmosphere. It is also an essential
  component of many of the chemical compounds that
  are vital to all living things. However,
  atmospheric nitrogen is not directly accessible
  to living things it is primarily in the form of
  N2, a molecule composed of two atoms of nitrogen
  linked by a triple bond. Because of the strength
  of this bond, large amounts of energy are
  required to free up the nitrogen atoms so that
  they can become part of the organic molecules of
  life.

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Reading Skills, continued

• NITROGEN FIXATION, continued
• When sufficient energy is added to N2 and
  hydrogen is present in the form of H2, the result
  is the compound ammonia, NH3. The nitrogen in
  ammonia is much more reactive than that in N2 and
  thus is much more readily available to living
  systems. The process of combining nitrogen and
  hydrogen into ammonia is an oxidation-reduction
  reaction known as nitrogen fixation. Nitrogen
  fixation is accomplished by certain
  microorganisms, which then feed nitrogen-rich
  compounds into the rest of the ecosystem.
  Nitrogen fixation is also done artificially at
  chemical plants where ammonia is made.

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Reading Skills, continued

• 6. In addition to being an oxidation-reduction
  reaction, what type of reaction is nitrogen
  fixation of N2 and H2 into NH3?
• A. a synthesis reaction
• B. a decomposition reaction
• C. a single-displacement reaction
• D. a double-displacement reaction

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Reading Skills, continued

• 6. In addition to being an oxidation-reduction
  reaction, what type of reaction is nitrogen
  fixation of N2 and H2 into NH3?
• A. a synthesis reaction
• B. a decomposition reaction
• C. a single-displacement reaction
• D. a double-displacement reaction

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Reading Skills, continued

• 7. Write the balanced chemical equation for
  nitrogen fixation.

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Reading Skills, continued

• 7. Write the balanced chemical equation for
  nitrogen fixation.
• Answer N2 3H2 ? 2NH3

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Interpreting Graphics
The graphics below plot energy changes during two
types of chemical reactions. Use these graphics
to answer question 8.
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Interpreting Graphics, continued

• 8. In each of these reactions, the chemical
  energy increases and then decreases during the
  course of the reaction. What does the height of
  the hill on each graph represent?
• A. energy that must be added to start the
  reaction
• B. energy released as reactant molecules
  approach one another
• C. the potential energy of the chemical bonds
  in the molecules of the reactants
• D. the change in total chemical energy between
  the reactants and the products

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Interpreting Graphics, continued

• 8. In each of these reactions, the chemical
  energy increases and then decreases during the
  course of the reaction. What does the height of
  the hill on each graph represent?
• A. energy that must be added to start the
  reaction
• B. energy released as reactant molecules
  approach one another
• C. the potential energy of the chemical bonds
  in the molecules of the reactants
• D. the change in total chemical energy between
  the reactants and the products

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Interpreting Graphics, continued
In hydrogen fuel cells, a catalyzed reaction
between hydrogen and oxygen gases forms water.
One of the diagrams below represents the balanced
chemical equation for this reaction. Use these
diagrams to answer question 9.
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Interpreting Graphics, continued

• 9. Which of the diagrams represents the balanced
  equation for the reaction?
• A. A C. C
• B. B D. D

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Interpreting Graphics, continued

• 9. Which of the diagrams represents the balanced
  equation for the reaction?
• A. A C. C
• B. B D. D