Advertisements
Advertisements
प्रश्न
A first order reaction takes 30 minutes for 50% completion. Calculate the time required for 90% completion of this reaction.
(log 2 = 0.3010)
Advertisements
उत्तर
For the given first−order reaction, the rate constant for 50% completion is given by
`k=2.303/t`
Here,
t=Time taken for 50% completion=30 min
[R]o=Initial concentration of the reactant
[R]=Final concentration of the reactant
Let [R]0 be 100 and due to 50% completion of reaction, [R] will be 100−50, i.e. 50.
Putting values in (i), we get
`k=2.303/30`
`=2.303/30`
For the same reaction, the time required for 90% completion of the reaction can be computed using the expression
`k=2.303/t`
Here,
[R]=Final concentration of reactant=100−90=10
(ii) Rate = `(Δ x)/(Δ t)`
= `2.303/k log10 = 2.303/k`
By putting the value of k here,we get
t = `(2.303 xx 1800)/(2.303 xx 0.3010)`
= `5.98 xx 10^3 "sec"`
APPEARS IN
संबंधित प्रश्न
The rate constant for a first order reaction is 100 s–1. The time required for completion of 50% of reaction is _______.
(A) 0.0693 milliseconds
(B) 0.693 milliseconds
(C) 6.93 milliseconds
(D) 69.3 milliseconds
During nuclear explosion, one of the products is 90Sr with half-life of 28.1 years. If 1μg of 90Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically.
Show that for a first order reaction half life is independent of initial concentration.
Which radioactive isotope would have the longer half-life 15O or 19O? (Given rate constants for 15O and 19O are 5.63 × 10–3 s–1 and k = 2.38 × 10–2 s–1 respectively.)
A sample of U238 (half-life = 4.5 × 109 years) ore is found to contain 23.8 g of U238 and 20.6 g of Pb206. The age of the ore is ______ × 109 years.
The half-life of cobalt 60 is 5.26 years. The percentage activity remaining after 4 years is ______%.
The rate of a first order reaction is 0.04 mol litre-1 s-1 at 10 minutes and 0.03 mol litre-1 sec-1 at 20 minutes after initiation. The half-life of the reaction is ______ min.
Assertion (A): The half-life of a reaction is the time in which the concentration of the reactant is reduced to one-half of its initial concentration.
Reason (R): In first-order kinetics, when the concentration of reactant is doubled, its half-life is doubled.
Calculate the half-life of a first order reaction from the rate constant given below:
2 min−1
A first order reaction takes 40 min for 30% decomposition. Calculate `"t"_(1/2)`.
