Collision Theory Of Chemical Reactions

Concept: Rate law:

Step 1: Write units of rate.


Step 2: For second order reaction ( ).


Step 3: Simplify units.

Concept:

Step 1: Substitute.

Step 1:



Step 2:


Step 3:


Step 4:
Final Answer:
Option (B)

Step 1: Understanding the Concept:
Arrhenius equation: . is frequency factor, is Boltzmann factor.

Step 2: Detailed Explanation:
The exponential term represents the fraction of molecules with energy . accounts for collision frequency and orientation.

Step 3: Final Answer:
The fraction of molecules with KE Ea is .

Step 1: Understanding the Concept:
A pseudo first order reaction is a reaction that is not truly first order but behaves like one because the concentration of one reactant is in large excess or remains constant.

Step 2: Detailed Explanation:
Inversion of cane sugar (sucrose) in the presence of an acid catalyst is a classic example. The reaction is: C H O + H O C H O (glucose) + C H O (fructose). Although two molecules are involved, the concentration of water is in large excess and remains effectively constant. Therefore, the rate depends only on the concentration of sucrose, making it pseudo first order.

Step 3: Final Answer:
Inversion of cane sugar is an example of a pseudo first order reaction.

Step 1: Understanding the Concept:
The integrated rate law for a first-order reaction is .

Step 2: Detailed Explanation:
Rearrange the integrated rate law to the form of a straight line (y = mx + c): Here, , (time), slope , and intercept .

Step 3: Final Answer:
The slope of the plot is .

Concept:
• Complex reactions involve multiple steps and intermediates

Step 1: Analyze reactions
(i) Oxidation of ethane → complex (multi-step)
(ii) Surface decomposition → simple
(iii) Saponification → simple
(iv) Nitration → complex mechanism
(v) Surface reaction → simple Final Conclusion:
Option (C)

Concept:

Step 1: Substitute values


Step 2: Solve
Final Conclusion:
Option (E)

Step 1: Understanding the Concept:
The order of a reaction dictates how sensitive the reaction rate is to changes in the concentration of the reactants. It is represented by the exponent in the rate law equation.

Step 2: Key Formula or Approach:
Write the generic rate law for a 3rd order reaction involving a single reactant. Then, substitute the new concentration to see how the overall rate changes.

Step 3: Detailed Explanation:
Let the initial concentration of the reactant be .
For a reaction that is overall 3rd order with respect to a single reactant, the rate law is:

The problem states that the concentration of the reactant is doubled.
Let the new concentration be .
Now, calculate the new rate using this new concentration:

Substitute into the equation:




Since is the initial rate, we have:

Therefore, the rate is increased 8 times.

Step 4: Final Answer:
The rate is increased 8 times.