Advertisements
Advertisements
Question
Solve
The half-life of a first-order reaction is 1.7 hours. How long will it take for 20% of the reactant to react?
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:
i. t1/2 = `0.693/"k"`
ii. `"t" = 2.303/"K" "log"_10 ["A"]_0/["A"]_"t"`
Calculation:
t1/2 = `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 32.9 min.
RELATED QUESTIONS
Answer the following in brief.
Obtain the relationship between the rate constant and half-life of a first-order reaction.
Derive the integrated rate law for the zeroth order reaction.
The rate of catalysed reaction is large than the uncatalysed reaction as _______.
For the reaction 2NOBr → 2NO2 + Br2, the rate law is rate = k[NOBr]2. If the rate of a reaction is 6.5 × 10–6 mol L–1 s–1, when the concentration of NOBr is 2 × 10–3 mol L–1. What would be the rate constant of the reaction?
A zero-order reaction \[\ce{X -> Product}\], with an initial concentration 0.02 M has a half-life of 10 min. if one starts with concentration 0.04 M, then the half-life is
This reaction follows first-order kinetics. The rate constant at particular temperature is 2.303 × 10−2 hour−1. The initial concentration of cyclopropane is 0.25 M. What will be the concentration of cyclopropane after 1806 minutes? (log 2 = 0.3010)
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.
The rate constant of a reaction is 5.8 × 10−2 s−1. The order of the reaction is ____________.
If 75% of a first order reaction was completed in 60 minutes, 50% of the same reaction under the same conditions would be completed in ____________.
Give two examples for zero order reaction.
A first order reaction has a rate constant 0.00813 min-1. How long will it take for 60% completion?
The time of completion of 90% of a first order reaction is approximately ____________.
A first order reaction completes its 10% in 20 minutes, then the time required to complete its 19% is ____________.
Which of the following represents the expression for `(3/4)^"th"` life of 1st order reaction?
The rate and the rate constants of the reaction, \[\ce{A + 2B -> C + D}\] are 8 × 10−3 mol dm−3 s−1 and 2 × 10−3 s−1 respectively. The concentrations of A and B are 4 mol dm−3 each. The overall order of the reaction is ____________.
Half-life period of a first order reaction, \[\ce{A -> product}\] is 3.0 hours. What is the value of rate constant?
For a first order reaction, \[\ce{A -> B}\], if [A] = 1 M and rate is 4 × 10−2 M s−1. What is the rate constant of the reaction?
0.0210 M solution of N2O5 is allowed to decompose at 43°C. How long will it take to reduce to 0.0150 M?
(Given k = 6.0 × 10−4 sec−1)
A first order reaction is 50% completed in 16 minutes. The percentage of reactant that will react in 32 minutes is ____________.
For the first order reaction A → B, the rate constant is 0.25 s-1, if the concentration of A is reduced to half, the value of rate constant will be ________.
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 \[\ce{X -> Y + Z}\] is 3 minutes. What is the time required to reduce the concentration of 'X' by 90 % of it's initial concentration?
Which is the unit of rate constant for the first-order reaction if time is expressed in seconds?
Obtain the expression for half-life and rate constant of the first-order reaction.
Which one of the following reactions is a true first-order reaction?
The rate constant for a first order reaction is 7.0 × 10-4 s-1. If initial concentration of reactant is 0.080 M, what is the half-life of reaction?
Calculate half-life of a first order reaction in minute if the rate constant is 1 × 10-3 s-1.
Calculate the time required to decrease the concentration of reactant of first order reaction from 0.8 M to 0.1 M if rate constant is 0.1155 hour−1.
