Advertisements
Advertisements
Question
The half-life period for the first order reaction is 1.7 hrs. How long will it take for 20% of the reactant to disappear?
Advertisements
Solution
Given: Half life (t1/2) = 1.7 hours, [A]0 = 100%, [A]t = 100 − 20 = 80%
To find: Time for 20% of reactant to react = t
Formulae:
- `"t"_(1/2) = 0.693/"k"`
- `"t" = 2.303/"K" log_10 ["A"]_0/["A"]_"t"`
Calculation: `"t"_(1/2) = 0.693/"k"`
k = `0.693/"t"_(1/2) = 0.693/(1.7 "h")` = 0.4076 h−1
t = `2.303/"k" log_10 ["A"]_0/["A"]_"t"`
= `2.303/(0.4076 "h"^-1) log 100/80`
t = `2.303/(0.4076 "h"^-1) xx 0.0969`
`= 0.5475 "h" xx (60 "min")/(1 "h")`
= 32.9 min
The time required for 20% of reaction to react is 0.5475 h or 32.9 min.
RELATED QUESTIONS
Answer the following in brief.
Derive the integrated rate law for the first-order reaction.
In a first-order reaction, the concentration of the reactant decreases from 20 mmol dm−3 to 8 mmol dm−3 in 38 minutes. What is the half-life of reaction?
Rate constant of a reaction is 3.6 × 10–3 s–1. The order of reaction is ______.
Write a mathematical expression for integrated rate law for zero-order reaction.
The rate constant of the first order reaction is 1.386 min–1. Calculate the time required for 80% reactant to decompose?
Derive an expression for the relation between half-life and rate constant for first-order reaction.
For a first-order reaction, the rate constant is 6.909 min−1 the time taken for 75% conversion in minutes is
Assertion: rate of reaction doubles when the concentration of the reactant is doubles if it is a first-order reaction.
Reason: rate constant also doubles.
Write the rate law for the following reaction.
A reaction that is `3/2` order in x and zero order in y.
Write the rate law for the following reaction.
A reaction that is second order in NO and first order in Br2.
Give two examples for zero order reaction.
The integrated rate law is a direct relationship between ____________ and ____________.
A first order reaction has rate constant 1 × 10−2 s−1. What time will, it take for 20 g or reactant to reduce to 5 g?
Which among the following reaction is an example of a zero order reaction?
The activation energy of a reaction is zero. Its rate constant at 280 K is 1.6 × 10-6 s-1, the rate constant at 300 K is ______.
In a first order reaction, the concentration of the reactant is reduced to 25% in one hour. The half-life period of the reaction is ____________.
The integrated rate equation for first-order reaction, A → product, is ______.
Half-life period of a first order reaction, \[\ce{A -> product}\] is 3.0 hours. What is the value of rate constant?
A first order reaction is 75% completed in 60 minutes, the time required for it's 50% completion is ____________.
A first order reaction takes 40 minutes for 30% completion. Calculate the half-life of reaction.
A certain zero order reaction has rate constant 0.025 M s-1. What will be the concentration of reactant 'A' after 15 seconds, if initial concentration is 0.50 M?
Half-life of first order reaction is 20 minutes. What is the time taken to reduce the initial concentration of the reactant to `1/10`th?
Obtain the expression for half-life and rate constant of the first-order reaction.
Which of the following reactions is not of the first order?
Calculate half-life of a first order reaction in minute if the rate constant is 1 × 10-3 s-1.
A radioactive isotope decayed to 17/32 of its original mass after 60 minutes. Find the half-life of this radioisotope.
What are integrated rate laws?
