Chemical Kinetics

Step 1: Identify Half-life
The concentration drops from 0.8 to 0.4 (half) in 15 minutes. Thus, the half-life ( ) is 15 minutes.
Step 2: Analyze Second Change
Concentration change: . This represents exactly two half-lives.
Step 3: Calculation
Total time .
Final Answer: (A)

Step 1: Understanding the Concept:
Set and solve for T.

Step 2: Detailed Explanation:




Taking natural log:
K.

Step 3: Final Answer:
1000 K

Step 1: Understanding the Concept:
Factors affecting reaction rate are temperature, concentration, nature of reactants, surface area, and catalyst. Molecularity is a theoretical concept.

Step 2: Detailed Explanation:
• (A) Molecularity: It is the number of molecules/atoms/ions colliding in an elementary step. It is a property of the reaction mechanism and does not determine the rate; it is not an influencing factor that can be changed. • (B) Temperature: Increasing temperature increases the rate. • (C) Concentration: Increasing concentration of reactants generally increases the rate. • (D) Nature of reactants: Ionic reactions are faster than covalent, etc.

Step 3: Final Answer:
Molecularity does not influence the rate of reaction, which corresponds to option (A).

Step 1: Understanding the Concept:
For a first-order reaction, the integrated rate law is .
Step 2: Detailed Explanation:
is the time when two-thirds of the reaction is complete, i.e., one-third remains. So, . Substituting ,
Step 3: Final Answer:
The correct expression is option (A).

Step 1: Understanding the Concept:
For first order, .
Step 2: Detailed Explanation:
For , . For , min.
Step 3: Final Answer:
Time required is min.

Step 1: Understanding the Concept:
Order = sum of exponents of concentration terms.
Step 2: Detailed Explanation:
Order = . Since 1 is not among the options, the answer is None of these.
Step 3: Final Answer:
The order is 1, which is not listed.

Step 1: Understanding the Concept:
Rate = .
Step 2: Detailed Explanation:

Multiply by :
Step 3: Final Answer:
.

Step 1: Understanding the Concept:
Catalyst provides alternative pathway.
Step 2: Detailed Explanation:
Adsorption weakens bonds, lowering activation energy.
Step 3: Final Answer:
Adsorption lowers activation energy.