Worksheet on chemical kinetics covering reaction rates, factors affecting reactions, and real-world applications.

Problem Analysis:

The provided document is a worksheet focused on the collision theory and its application to understanding how reaction rates are affected by various factors such as temperature, pressure, surface area, concentration, and catalysts. The questions aim to test the student's understanding of these concepts and their ability to apply them in different scenarios.

Solution and Explanation:

#### 1. A study of reaction rate is called chemical kinetic.
- Answer: Correct.
- Explanation: The study of reaction rates is indeed referred to as chemical kinetics. This field examines how fast chemical reactions occur and what factors influence their rates.

#### 2. Reaction rate refers to how quickly or slowly the reactants disappear and the products appear. It is measured in terms of the energy of the reactants.
- Answer: Partially correct.
- Explanation: The first part is correct: the reaction rate refers to how quickly reactants are consumed and products are formed. However, the second part is incorrect. Reaction rates are not measured in terms of the energy of the reactants. Instead, they are typically measured in terms of the change in concentration of reactants or products over time (e.g., moles per liter per second, mol/L·s).

#### 3. If a reaction is to occur, reacting particles must first collide and this collision must be effective.
- Answer: Correct.
- Explanation: According to the collision theory, for a reaction to occur, the reacting particles must collide with each other. Additionally, the collision must have enough energy (activation energy) and the correct orientation to result in a successful reaction.

#### 4. What are the five major factors that affect reaction rate?
- Answer: Pressure, temperature, concentration, catalyst, and surface area.
- Explanation: These are the primary factors that influence reaction rates:
- Pressure: Affects the rate of gas-phase reactions by changing the frequency of collisions.
- Temperature: Increases the kinetic energy of particles, leading to more frequent and energetic collisions.
- Concentration: Higher concentrations lead to more frequent collisions between reactant particles.
- Catalyst: Lowers the activation energy, increasing the number of effective collisions.
- Surface Area: Larger surface areas increase the number of available sites for reactions to occur.

#### 5. Why would a mixture of gases react faster when the volume they occupy is decreased?
- Answer: There will be less space for the particles to move, therefore the amount of collisions between the gas particles will increase.
- Explanation: When the volume of a gas mixture is decreased, the particles are forced closer together. This increases the frequency of collisions between the reactant particles, leading to a faster reaction rate.

#### 6. Why would iron fillings rust faster than an iron nail?
- Answer: The iron fillings have a larger surface area than the iron nail, therefore the amount of collisions between air particles and iron will be greater.
- Explanation: Rusting is a chemical reaction involving iron, oxygen, and water. A larger surface area means more iron atoms are exposed to the reactants (oxygen and water), leading to more frequent collisions and a faster reaction rate. Iron fillings have a much larger total surface area compared to a solid iron nail.

#### 7. What is the effect of a catalyst on the required energy to achieve effective collisions?
- Answer: A catalyst will lower the activation energy of the reaction.
- Explanation: Catalysts work by providing an alternative reaction pathway with a lower activation energy. This allows more collisions to be effective, increasing the reaction rate without being consumed in the process.

#### 8. Enzymes act as catalysts in our bodies. Have you ever noticed that your hands seem to get “stiff” when they get cold? The reason is that these enzyme reactions causing the muscles to contract slow down when your hands are cold so you can’t contract your muscles as fast and your hands feel stiff! Decreasing temperature decreases the rate of reaction.
- Answer: Correct.
- Explanation: Enzymes are biological catalysts that speed up biochemical reactions in living organisms. When the temperature decreases, the kinetic energy of the molecules decreases, leading to fewer and less energetic collisions. This results in a slower reaction rate, which can manifest as stiffness in muscles due to reduced enzyme activity.

#### 9. Enzymes are in molds and bacteria that spoil food. Explain using your knowledge of factors affecting the rate of reaction, why food doesn’t spoil as fast when it is refrigerated as it would at room temperature.
- Answer: When food is refrigerated, the temperature drop causes the particles to slow down and decreases the amount of collisions between particles, thus decreasing the rate of the spoilage for the food.
- Explanation: Refrigeration lowers the temperature, reducing the kinetic energy of the molecules involved in the spoilage process (e.g., enzymes in molds and bacteria). With less kinetic energy, there are fewer and less energetic collisions between reactant particles, leading to a slower reaction rate and reduced spoilage.

Final Answer:

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