List of top Chemistry Questions on Half life

The half-life of a radioactive substance is 10 days. After 30 days, fraction remaining is:
The half-life of a first-order reaction is:
Calculate the half-life of a first-order reaction if the rate constant is \(0.693\, \text{min}^{-1}\).
A first order reaction is 75% completed in 1000 s at 300 K. What is its half-life period at 300 K?
The time needed for completion of 80% is \( y \) times the half-life period of a first order reaction. What is the value of \( y \)?
What is half life of a first order reaction if time required to decrease concentration of reactant from 0.4 M to 0.1 M is $x$ hour?
What is the half life period of the first order reaction whose rate constant is \(2.31 \times 10^{- 1} \mathrm{~s}^{- 1}\)
What is rate constant of a first order reaction having half life \(138.6 \text{ minute}\)?
For a first order reaction, time required for 99% completion is \(x\) times the time required for 90% completion. Find \(x\).
Half life of a first order reaction is \(36\;hr\). Find out time (in hour) required for concentration of reactant to get reduced by \(90\%\).
The number of incorrect statement/s from the following is ____ .
A. The successive half lives of zero order reactions decreases with time.
B. A substance appearing as reactant in the chemical equation may not affect the rate of reaction.
C. Order and molecularity of a chemical reaction can be a fractional number.
D. The rate constant units of zero and second order reaction are mol L–1s–1 and mol–1 Ls–1 respectively.
At 30ºC, the half life for the decomposition of \(AB_2\) is 200 s and is independent of the initial concentration of \(AB_2\). The time required for 80% of the \(AB_2\) to decompose is(Given : \(log\; 2 = 0.30,\; log \;3 = 0.48\))
The rate constant of a first order reaction is \(231\times10^{-5}\ s^{-1}\). How long will 4 g of this reactant reduce to 2 g?
The half-life of \( _{43}\text{Tc}^{99} \) is 6 hours. If 12 mg of \( _{43}\text{Tc}^{99} \) is injected to a patient, after 24 hours how much Tc will be left in the patient’s body? (A) 0 mg
Calculate the half-life of a first order reaction if the rate constant of the reaction is $2.772 \times 10^{-3}\,\text{s}^{-1}$.
The half-life of a first order reaction is 6.0 hours. How long does it take for 60% of the reactant to disappear?
A certain radioactive isotope \( ^A_Z X \) (half-life = 10 days) decays to give \( ^{A-4}_{Z-2} X \). If 1.0 g of \( X \) is kept in a sealed vessel, find the volume of He accumulated at STP in 20 days. (Molar mass of \( ^A_Z X = 253 \))
Given a sample of radium-226 having half-life of 4 days. Find probability that a nucleus disintegrates after 2 half-lives.
Two substances R and S decompose in solution independently, both following first order kinetics. The rate constant of R is twice that of S. Initially 0.5 millimoles of R and 0.25 of S. The molarities of R and S will be equal at the end of time equal to:
Determine the \(\mathrm{pH}\) of \(0.024\mathrm{\ M}\) hydroxylamine hydrochloride solution. (\(K_b\) of hydroxyl amine is \(10^{-8}\))
Determine solubility of \(\mathrm{AgBr}\) in a \(0.1\mathrm{\ M\ KCN}\) solution. \([K_f \text{ of } [\mathrm{Ag(CN)_2}]^- = 5.6 \times 10^8; K_{sp} \text{ of } \mathrm{AgBr} = 7.7 \times 10^{-13}]\)
Radioactive decay is a:
The rate constant for the first order reaction is 60 s\(^{-1}\). How much time will it take to reduce the concentration of the reactant to \( \frac{1}{16} \)th value?