Advertisements
Advertisements
Question
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?
Advertisements
Solution 1
Given: [A]0 = 0.8 M, [A]t = 0.2 M, t = 12 hours
To find: Half life of reaction (t1/2)
Formulae:
- k = `2.303/"t" log_10 (["A"]_0)/(["A"]_"t")`
- `"t"_(1/2) = 0.693/"k"`
Calculation: Substituting given value in
k = `2.303/"t" log_10 (["A"]_0)/(["A"]_"t")`
k = `2.303/(12 "hr") log_10 0.8/0.2`
= `2.303/(12 "hr") log_10 (4)`
= `2.303/(12 "hr") xx 0.6020`
= Antilog10 (log10 2.303 + log10 0.6020 − log10 12)
= Antilog10 (0.3623 + `bar(1).7796` − 1.0792 )
= Antilog10 `(bar(1).0627 )`
= 0.1115 hr–1
`"t"_(1/2) = 0.693/"k" = 0.693/(0.1155 "hr"^-1)` = 6 hr
Solution 2
Concentration is reduced to 25%. It means it takes two half-lives to decrease the concentration of reactant from 0.8 M to 0.2 M in first-order reaction. Hence, half-life of the reaction is 12/2 = 6 hours.
The half life of reaction is 6 hours.
APPEARS IN
RELATED QUESTIONS
Answer the following in brief.
Obtain the relationship between the rate constant and half-life of a first-order reaction.
How will you represent first order reactions graphically.
Derive the integrated rate law for the zeroth order reaction.
Answer the following in brief.
Give one example and explain why it is pseudo-first-order.
Explain pseudo first order reaction with a suitable example.
The rate constant of the first order reaction is 1.386 min–1. Calculate the time required for 80% reactant to decompose?
For a first-order reaction \[\ce{A -> B}\] the rate constant is x min−1. If the initial concentration of A is 0.01 M, the concentration of A after one hour is given by the expression.
For a first-order reaction, the rate constant is 6.909 min−1 the time taken for 75% conversion in minutes is
Write the rate law for the following reaction.
A reaction that is second order in NO and first order in Br2.
A zero order reaction is 20% complete in 20 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?
For first order reaction the concentration of reactant decreases from 0.2 to 0.1 M in 100 minutes. What is the rate constant of the reaction?
For the first order reaction, plot of log10 [A]t against time 't' is a straight line with a negative slope equal to ____________.
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 zero order reaction, the plot of [A]t vs t is linear. The slope of the line is equal to ____________.
The time taken for 80% of a first order reaction to be complete is approximately ____________.
A first order reaction takes 40 minutes for 30% decomposition. What is the half-life of reaction?
A first order reaction is 50% completed in 16 minutes. The percentage of reactant that will react in 32 minutes is ____________.
What is the unit of rate constant for the zero order reaction?
Which is the unit of rate constant for the first-order reaction if time is expressed in seconds?
The rate constant and half-life of a first order reaction are related to each other as ______.
Which of the following correctly represents integrated rate law equation for a first order reaction in a gas phase?
A first order reaction takes 10 minute for 30% completion. Find rate constant of the reaction.
The plot that represents the zero order reaction is:
If the half-life of a first-order reaction is 10 minutes, find the time required to decrease the concentration of the reactant from 0.08 M to 0.02 M.
