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.
Answer the following in brief.
Derive the integrated rate law for the first-order reaction.
How will you represent first order reactions graphically.
Answer the following in brief.
What is a zeroth-order reaction?
Give one example of a pseudo first-order reaction.
What is half life of first order reaction if time required to decrease concentration of reactants from 0.8 M to 0.2 M is 12 hours?
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?
The rate constant of the first order reaction is 1.386 min–1. Calculate the time required for 80% reactant to decompose?
Describe the graphical representation of first order reaction.
Give two examples for zero order reaction.
The time for half change in a first order decomposition of a substance A is 60 seconds. Calculate the rate constant. How much of A will be left after 180 seconds?
A first order reaction is 40% complete in 50 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?
The integrated rate law is a direct relationship between ____________ and ____________.
A first order reaction has a rate constant 0.00813 min-1. How long will it take for 60% completion?
A reaction that is of the first order with respect to reactant A has a rate constant 6 min−1. If we start with [A]0 = 0.5 mol dm−3, when would [A] reach the value 0.05 mol dm−3?
Half-life period of a first order reaction, \[\ce{A -> product}\] is 3.0 hours. What is the value of rate constant?
In the reaction \[\ce{2SO2 + O2 -> 2SO3}\] the rate of appearance of SO3 is 4 × 10−4 M/s, the rate of disappearance of O2 is ____________.
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?
Which among the following is an example of pseudo first order 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)
The time required to decompose SO2Cl2 to half of it's initial amount is 60 minutes. Calculate rate constant for this first order reaction.
A first order reaction, A → B takes 100 minutes for it's 90% completion. What is the rate constant of reaction?
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 of the following reactions is not of the first order?
Which is the relation between half life and rate constant for a zero order?
Consider the following reaction.
\[\ce{SO2(g) + 1/2 O2(g) <=>[K1] SO3(g)}\]
\[\ce{2SO3(g)<=>[K2] 2SO2(g) + O2(g)}\]
What is the relation between K1 and K2?
A radioactive isotope decayed to 17/32 of its original mass after 60 minutes. Find the half-life of this radioisotope.
The half-life of first order reaction is 1.7 hour. What is its rate constant?
For a first order reaction, the plot of log k against 1/T is a straight line. The slope of the line is equal to ______.
