Previous Year NEET Question- Chemical Kinetics

• NEET 2018:

A first order reaction is 50% completed in 30 minutes. Calculate the time required for 90% completion of the reaction.

Solution:

The formula for the time taken for the completion of a first order reaction is:

t = (2.303)/(k) log([A]0/[A])

Where,

• t is the time taken for the completion of the reaction
• k is the rate constant of the reaction
• [A]0 is the initial concentration of the reactant
• [A] is the concentration of the reactant at time t

In this case, the initial concentration of the reactant is [A]0 = 100% and the concentration of the reactant at 50% completion is [A] = 50%. So, we can substitute these values into the equation to find the rate constant:

t = (2.303)/(k) log(100/50)

t = (2.303)/(k) log(2)