Chemical Kinetics - SS2 Chemistry Past Questions and Answers - page 5
The rate constant (k) for a second-order reaction is 0.005 M-1s-1. If the initial concentration of the reactant is 0.20 M, calculate the concentration after 60 seconds.
For a second-order reaction, the rate equation is given by:
rate = k[A]2
We can rearrange the equation to solve for the concentration:
rate = k[A]2
[A]2 = rate / k
[A] = sqrt(rate / k)
Given that the rate constant (k) is 0.005 M-1s-1 and the initial concentration ([A]₀) is 0.20 M, we can substitute these values into the equation:
[A] = sqrt(rate / k) = sqrt([A]₀2 - 2kt)
[A] = sqrt((0.20 M)2 - 2 x 0.005 M-1s-1 x 60 s)
[A] ≈ 0.173 M
Therefore, the concentration of the reactant after 60 seconds is approximately 0.173 M.
According to collision theory, what is required for a chemical reaction to occur?
Heat energy
Light energy
Collision between reactant particles
Catalysts
The activation energy of a reaction is defined as:
The energy released during a reaction
The energy required to initiate a reaction
The energy change when reactants are converted to products
The energy difference between the highest and lowest energy states of reactants
How does an increase in temperature affect the rate of a chemical reaction, according to collision theory?
It decreases the rate of reaction
It has no effect on the rate of reaction
It increases the rate of reaction
It depends on the specific reaction
Which of the following factors does NOT influence the rate of chemical reactions according to collision theory?
Concentration of reactants
Temperature
Surface area of reactants
Volume of reactants
How does a catalyst affect the rate of a chemical reaction, based on collision theory?
It lowers the activation energy of the reaction
It increases the activation energy of the reaction
It changes the stoichiometry of the reaction
It has no effect on the rate of reaction
Which of the following statements is true regarding collision theory?
All collisions between reactant particles result in a chemical reaction
The total number of collisions between reactant particles is irrelevant to the reaction rate
Successful collisions result in the formation of products
Only high-energy collisions contribute to the reaction rate
How does an increase in reactant concentration affect the rate of a chemical reaction, according to collision theory?
It decreases the rate of reaction
It has no effect on the rate of reaction
It increases the rate of reaction
It depends on the specific reaction
What is the role of proper orientation in collision theory?
It determines the temperature at which a reaction occurs
It ensures that reactant particles collide with sufficient energy
It influences the rate of reaction through the alignment of reactant molecules during collisions
It is unrelated to the rate of reaction
Explain the principles of collision theory and how it relates to the rate of chemical reactions.
Collision theory is a fundamental concept in understanding the rate of chemical reactions. It proposes that for a reaction to occur, reactant particles must collide with sufficient energy and proper orientation. The collision theory provides the following principles:
a. Collision Frequency: For a reaction to take place, reactant particles must collide. The collision frequency is determined by the concentrations of the reactants and their molecular speeds. Higher concentrations and increased kinetic energy (temperature) lead to more frequent collisions.
b. Activation Energy: Reactant particles must possess a minimum amount of energy, known as the activation energy, to initiate a reaction. The activation energy is required to break the existing chemical bonds and allow new bonds to form. Only collisions with sufficient energy equal to or greater than the activation energy result in a reaction.
c. Effective Collisions: Not all collisions lead to a reaction. For a collision to be effective, the colliding particles must have the proper orientation. This ensures that the necessary bond-breaking and bond-forming processes occur during the collision.
Based on collision theory, increasing the concentration of reactants or raising the temperature increases the collision frequency, leading to a higher rate of reaction. Additionally, a higher temperature provides more energy to reactant particles, increasing their kinetic energy and the likelihood of collisions with sufficient energy to overcome the activation energy barrier.