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Jonathan Nichols edited Intro1.tex
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\frac{-dA}{dt}=\omega[A]
\end{equation}
The time dependent rate coefficient, k(t), is determined by integrating the rate law of the reaction and forming a survival function from the integrated rate law.
The survival function is simply a measure of a the cocentration of species at some time compared to its initital concentration.
\begin{equation}
S(t)=\frac{[A]_t}{[A]_0}
\end{equation}
From the survival function, the time dependent rate coefficient is determined by taking various time derivatives of the survival function, depending on the total order of reaction. For first order irreversible decay reactions, the time dependent rate coefficient is the negative time derivative of the natural log of the survival function[insert citation]
\begin{equation}
\frac{-dlnS(t)}{dt}=k(t)
\end{equation}
In order to determine the time dependent rate coefficient in higher order reactions, it is useful to use the survival function, but is not necessary. The survival function of any reaction involving any number of the same molecule can be derived using the integrated rate laws of reactions. For example, the
second $n^t{h}$ order integrated rate law
is is, where $A+nA\rightarrow B$.
\begin{equation}
[A_t]=\frac{[A_0]}{1+\omega t[A_0]} \frac{1}{[A_t]^{n-1}}=\frac{1}{[A_0]^{n-1}}+(n-1)\omega t
\end{equation}
The second order From the integrated rate law, we get the survival function
is
\begin{equation}
S(t)=\frac{[A_t]}{[A_0]}=\frac{1}{1+\omega t[A_0]} S(t)=\frac{[A_t]}{[A_0]}\sqrt[n-1]{\frac{1}{1+(n-1)\omega t[A_0]^{n-1}}}
\end{equation}
From
this survival function, taking the inverse of the survival
function and then the time derivative yields function, the time dependent rate
coefficient. coefficient is
\begin{equation}
k(t)=\left(\frac{dS(t)^{-1}}{dt}\right) k(t)=(\frac{d\frac{1}{(S(t)^{n-1)}}}{dt})
\end{equation}
The same can be derived for $n^{th}$ Taking our definitions of the integrated rate law, survival function, and time dependent rate coefficient, we are able to apply them to to second order
reactions, where $A+nA\rightarrow B$. irreversible decay. The integrated rate law
of these reactions in second order is
\begin{equation}
\frac{1}{[A_t]^{n-1}}=\frac{1}{[A_0]^{n-1}}+(n-1)\omega t [A_t]=\frac{[A_0]}{1+\omega t[A_0]}
\end{equation}
From the integrated rate law, we get the The second order survival function
is
\begin{equation}
S(t)=\frac{[A_t]}{[A_0]}\sqrt[n-1]{\frac{1}{1+(n-1)\omega t[A_0]^{n-1}}} S(t)=\frac{[A_t]}{[A_0]}=\frac{1}{1+\omega t[A_0]}
\end{equation}
From
the this survival function,
taking the inverse of the survival function and then the time derivative yields the time dependent rate
coefficient is coefficient.
\begin{equation}
k(t)=(\frac{d\frac{1}{(S(t)^{n-1)}}}{dt}) k(t)=\left(\frac{dS(t)^{-1}}{dt}\right)
\end{equation}
When it comes to mixed second order reactions, the rate law does not allow a survival function to be obtained for the process because the rate law only allows the survival function of one reactant to be looked at. The rate law of a mixed second order reaction is
\begin{equation}
\int\frac{dx}{([A_0]-x)([B_0]-x)}=k(t)