Version Conflict: zero order reactions

Here are 5 questions based on the provided text on zero order reactions — suitable for Class 12 Chemistry (CBSE pattern):

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🔹 Conceptual and Numerical Questions on Zero Order Reactions

1. Very Short Answer (1 Mark):
   Q1. Write one example of a zero order reaction that occurs on a metal surface.
   Ans: Decomposition of NH₃ on a hot platinum surface.

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2. Short Answer (2 Marks):
   Q2. Why is the rate of a zero order reaction independent of the concentration of reactant?
   Ans: In a zero order reaction, the rate is constant and does not depend on the concentration of reactant because the reaction surface (such as a metal catalyst or enzyme) is saturated. Hence, even if concentration increases, the rate remains unchanged.

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3. Numerical (3 Marks):
   Q3. For a zero order reaction, the initial concentration of a reactant is 0.6 mol/L. After 30 seconds, it becomes 0.3 mol/L. Calculate the rate constant .
   

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4. Application-Based (2 Marks):
   Q4. Why do enzyme-catalyzed reactions often show zero order kinetics at high substrate concentration?
   Ans: Because at high substrate concentration, all the active sites of the enzyme become saturated. Beyond this point, increasing substrate concentration does not increase the rate — hence, the reaction becomes zero order.

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5. Chemical Equation-Based (1 Mark):
   Q5. Write the balanced chemical equation of the decomposition of ammonia over a platinum catalyst that shows zero order kinetics.

🔹 Numerical Questions on Zero Order Reactions

Q6. In a zero order reaction, the initial concentration of the reactant is 0.5 mol/L. After 20 seconds, the concentration drops to 0.35 mol/L. Calculate the rate constant and determine how long it will take for the concentration to reach 0.1 mol/L.

Q7. For a zero order reaction, the rate constant is . If the initial concentration of the reactant is 0.8 mol/L, calculate the time required for the concentration to drop to 0.2 mol/L.

Q8. A zero order reaction is 40% complete in 25 seconds. Calculate the initial concentration of the reactant if the rate constant is .

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