JEE Main On 16 April 2018 Question 20
Question: If 50 % of a reaction occurs in 100 second and 75% of the reaction occurs in 200 second, the order of this reaction is: [JEE Main 16-4-2018]
Options:
A) 1
B) Zero
C) 2
D) 3
Show Answer
Answer:
Correct Answer: A
Solution:
- 50% of a reaction occurs in 100 second and 75% of the reaction occurs in 200 second, the order of this reaction is 1. Let the initial reactant concentration is 1 M. In first 100 seconds, reactant concentration is reduced to 50% or $ 1\times \frac{50}{100}=0.5,M. $ In second 100 seconds (total 200 seconds from start), reactant concentration is reduced to $ 100-75=25% $ or $ 1\times \frac{25}{100}=0.25,M. $ Thus we observe that after each 100 second period, the reactant concentration is reduced to one half. Hence, 100 second is half-life period and is independent of reactant concentration. This is characteristic of first order reaction.
