Chemical Reactions
Chemical Reactions
Preview
• Understanding Concepts
• Reading Skills
• Interpreting Graphics
Standardized Test Prep
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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.
Chemical Reactions
Standardized Test Prep
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.
Chemical Reactions
Standardized Test Prep
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.
Chemical Reactions
Standardized Test Prep
Understanding Concepts, continued
5. In the redox reaction H2 + F2 → 2HF, which element is
reduced, and which is oxidized?
Chemical Reactions
Standardized Test Prep
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.
Chemical Reactions
Standardized Test Prep
Reading Skills
NITROGEN FIXATION
The element nitrogen makes up about 78% of Earth’s
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.
Chemical Reactions
Standardized Test Prep
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 oxidationreduction 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.
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
Reading Skills, continued
7. Write the balanced chemical equation for nitrogen
fixation.
Chemical Reactions
Standardized Test Prep
Reading Skills, continued
7. Write the balanced chemical equation for nitrogen
fixation.
Answer: N2 + 3H2 → 2NH3
Chemical Reactions
Standardized Test Prep
Interpreting Graphics
The graphics below plot energy changes during two types of
chemical reactions. Use these graphics to answer question 8.
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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
Chemical Reactions
Standardized Test Prep
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.
Chemical Reactions
Standardized Test Prep
Interpreting Graphics, continued
9. Which of the diagrams represents the balanced
equation for the reaction?
A. A
C. C
B. B
D. D
Chemical Reactions
Standardized Test Prep
Interpreting Graphics, continued
9. Which of the diagrams represents the balanced
equation for the reaction?
A. A
C. C
B. B
D. D