CH142 Exam 1 Sample Solutions provides detailed answers to various chemistry problems, including reaction mechanisms, rate laws, and equilibrium constants. This resource is designed for students preparing for their CH142 exam, covering essential topics such as Arrhenius plots, reaction rates, and the impact of catalysts. The solutions include step-by-step explanations and calculations relevant to the course material. Ideal for students seeking to enhance their understanding of chemical kinetics and thermodynamics.

Key Points

  • Includes solutions for reaction mechanisms and rate laws in CH142.
  • Covers equilibrium constants and their calculations for various reactions.
  • Explains the effect of temperature on reaction rates using Arrhenius plots.
  • Provides insights into the decomposition of ozone and its environmental impact.
Malik Jett
8 pages
Exams
Malik Jett
8 pages
Exams
43
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CH 142 Exam 1 Sample Solutions
1. The energy profiles for four different reactions (a, b, c, and d) are shown in the adjacent figure. The
scales are the same for each.
C. The following figure shows four different Arrhenius plots corresponding to the four different
reactions above. Fill in the blanks below with the reaction (a, b, c, or d) that corresponds to that
line on the Arrhenius plot.
2. Chlorofluorocarbons released into the atmosphere from refrigerants and aerosol sprays were found to
catalyze the decomposition of ozone, leading to the formation of an ozone hole over the South Pole. The
catalyzed reaction was found to have an activation energy of 2.2 kJ/mol compared with an activation
energy of 17.7 kJ/mol for the uncatalyzed reaction. By what factor is the decomposition rate constant
increased in the catalyzed reaction at 200 K, the temperature of the stratosphere?
Uncatalyzed:
Catalyzed:
2
3. The process NO
2
(g)+ O
3
(g) → NO
3
(g)+ O
2
(g) reacts twice as fast at 52.5°C as it does at 25.0 °C.
How much faster (relative to 25.0°C) does this process react at 80.0 °C?
4. A reaction has the following three mechanistic steps:
A. What is the overall reaction that corresponds to this mechanism?
B. Identify each species in the mechanism as a reactant, product, intermediate, or catalyst.
3
C. If the rate law for this reaction is, rate = k[CHCl
3
][Cl
2
]
1/2
, which is the slow (i.e. rate-limiting)
step?
5. At a certain temperature, a 1.00-L flask initially contained 0.298 mol PCl
3
(g) and 8.70 x 10
-3
mol
PCl
5
(g). After the system reached equilibrium, 2.00 x 10
-3
mol Cl
2
(g) was present. Calculate K
C
at
this temperature for the reaction:
6. The data in the table below were obtained for the reaction:
2 ClO
2
(aq) + 2 OH- (aq) → ClO
3
- (aq) + ClO
2
- (aq) + H
2
O (1)
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FAQs

What topics are covered in the CH142 Exam 1 Sample Solutions?
The CH142 Exam 1 Sample Solutions cover a variety of essential chemistry topics, including reaction mechanisms, rate laws, and equilibrium constants. Specific areas of focus include the Arrhenius equation and its application to reaction rates, as well as the impact of catalysts on reaction kinetics. Additionally, the solutions address the decomposition of ozone and the role of chlorofluorocarbons in environmental chemistry, providing a comprehensive overview for students preparing for their exams.

How does temperature affect reaction rates according to the solutions?
The solutions illustrate that temperature significantly impacts reaction rates, as shown through the Arrhenius equation. For instance, the document discusses how increasing temperature generally increases the rate constant, leading to faster reactions. It also provides specific examples, such as the comparison of reaction rates at different temperatures, demonstrating the relationship between temperature and kinetic energy of molecules.

What is the significance of catalysts in chemical reactions?
Catalysts play a crucial role in chemical reactions by lowering the activation energy required for the reaction to proceed. The solutions detail how the presence of a catalyst can significantly increase the rate of a reaction, as seen in the examples provided. This is particularly important in industrial applications where catalysts can enhance efficiency and reduce energy costs.

What calculations are included in the sample solutions?
The sample solutions include various calculations related to reaction rates, equilibrium constants, and activation energies. For example, students will find detailed steps for calculating the equilibrium constant for specific reactions and determining the concentration of reactants and products at equilibrium. These calculations are essential for understanding the quantitative aspects of chemical reactions.

How are reaction mechanisms explained in the solutions?
The solutions explain reaction mechanisms by breaking down complex reactions into individual steps, identifying reactants, products, intermediates, and catalysts. Each step is analyzed to show how they contribute to the overall reaction rate. This detailed approach helps students grasp the intricacies of chemical processes and the factors influencing them.