Recent questions tagged half-life

A certain reaction is first order, and 540 s after initiation of the reaction, 32.5% of the reactant remains. At what time after initiation of the reaction of the reaction will 10% of the reactant remain?

asked Jul 25, 2014 by balaji.thirumalai

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A certain first order reaction is 45% complete in 65 seconds. Determine the rate constant and the half-life for this process.

asked Jul 25, 2014 by balaji.thirumalai

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Calculate half-life for first-order reaction if 68% of a substance is reacted within 66 s.

asked Jul 25, 2014 by balaji.thirumalai

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What is the concentration of $A$ at time $45\;s$ if $[A]_o = 1\;M$, $[B]_o = 45\;M$, and 2nd order rate constant is $0.6\;M^{-1}s^{-1}$?

asked Jul 25, 2014 by balaji.thirumalai

1 answer

If $[A] = 55\;M$ at $39s$, $[A]_o = 99\;M$, and $[B]_o = 1000\;M$, what is the 2nd order reaction rate constant?

asked Jul 25, 2014 by balaji.thirumalai

1 answer

The thermal decomposition of phosphine to phosphorus and hydrogen gas is a first order reaction, with a half-life of 35 s at 680$^\circ$C. Calculate the time required for 95% of phosphine to decompose.

asked Jul 24, 2014 by balaji.thirumalai

1 answer

The thermal decomposition of N$_2$O$_5$ to form NO$_2$ and O$_2$ is a first order reaction. The rate constant for the reaction is $5.1x10^{–4}s^{-1}$ at $318^{\circ} K$. Calculate the half-life of this reaction.

asked Jul 24, 2014 by balaji.thirumalai

1 answer

A certain first order reaction proceeds through t first order kinetics. The half-life of the reaction is 180 s. What percent of the initial concentration remains after 900s?

asked Jul 24, 2014 by balaji.thirumalai

1 answer

A first order reaction has a rate constant of $1.00\;s^{-1}$. What is the half life of the reaction?

asked Jul 24, 2014 by balaji.thirumalai

1 answer

The half life of $\;^{215}At\;$ is $\;200 \mu s\;$ . The time taken for radioactivity of a sample of $\;^{215}At\;$ to decay to $\;{\large\frac{1}{4}}^{th}\;$ of its initial value is

asked Mar 11, 2014 by yamini.v

1 answer

The half life of radioactive radon is 3.8 days . The time , at end of which $\;\large\frac{1}{20}^{th}\;$ of radon sample will remain undecayed is

asked Feb 27, 2014 by yamini.v

1 answer

A radioactive nucleus can decay by two different process . The half life for first process is $\;t_{1}\;$ and that for second process is $\;t_{2}\;$. Find the effective half life of nucleus

asked Feb 27, 2014 by yamini.v

1 answer

The disintegration rate of a radioactive sample at a certain instant is 4750 dpm . Five minute later rate becomes 2700 disintegration per minute ; Then the half-life of sample is

asked Feb 27, 2014 by yamini.v

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What is the relation between half life ($t_{1/2}$) and temperature for an $n^{th}$ order reaction ;$n > 2$

asked Dec 19, 2013 by sreemathi.v

1 answer

The ratio of $\large\frac{t_{1/2}}{t_{3/4}}$ for $n^{th}$ order is

asked Dec 19, 2013 by sreemathi.v

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The inactivation of a viral preparation is found to be first order reaction.If in beginning $1.5\%$ of virus is inactivated then calculate time required for 50V inactivation.

asked Dec 19, 2013 by sreemathi.v

1 answer

An optically active compound A upon acid catalyzed hydrolysis yield two optically active compound B & C by first order kinetics.It is given that $[\alpha_0]$ for $A,B$ & C are $60^o,40^o$ & $-80^o$ respectively.If observed both of the mixture after 20 minute was $5^o$ while after completion of the reaction it was $-20^o$.What is $t_{1/2}$ of reaction?

asked Dec 18, 2013 by sreemathi.v

1 answer

The half life of carbon is 5730years.Approximately how many years will it take for 94% of a sample to decay?

asked Dec 18, 2013 by sreemathi.v

1 answer

The decomposition of hydrogen bromide into hydrogen and iodine is second order reaction.The reaction rate constant is $K=0.08Lmol^{-1}s^{-1}$.How long it take an initial concentration of 0.04M to decrease to half this concentration?

asked Dec 18, 2013 by sreemathi.v

1 answer

If a reactant is used up according to a first order rate equation and initial concentration of reactant is $32mol\;L^{-1}$ what is concentration of reactant after six half lives have passed?

asked Dec 18, 2013 by sreemathi.v

1 answer

The rate constant for a first order reaction is $20hr^{-1}$.The half life of the reaction will be

asked Dec 16, 2013 by sreemathi.v

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A first order reaction is represented by which of the following graphs?

asked Dec 13, 2013 by sreemathi.v

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What is the half-life of a reaction with $[A]_o = 109\;M$, $[B]_o = 1\;M$, $k' = 45M^{-1}s^{-1}$ ?

asked Dec 13, 2013 by sreemathi.v

1 answer

A graph between $1/[A]^2$ vs t is plotted below where [A] is conc of [A] at time t and $[A_o]$ is initial conc and K is the rate constant of a $Rx^n$ $nA\rightarrow$ product. What is the half life for the $Rx^n(t_{\large\frac{1}{2}})$

asked Dec 12, 2013 by sreemathi.v

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