I need to calculate the half life for a first order reaction for which I need the rate constant $k$. From literature I observed that for a very closely simulated experiment I obtained the numerical value of $k$ but the unit of $k$ was given in $\frac1{\mathrm s}\cdot\frac1{\mathrm{kPa}}$.

I am only familiar with $k$ in $\frac1{\mathrm s}$. from which I can easily estimate the $t_{1/2}$.

Can somebody please explain how I convert the $\frac1{\mathrm s}\cdot\frac1{\mathrm{kPa}}$ unit to $\frac1{\mathrm s}$.

Additional informaton: The laboratory experiment was conducted at approx $85\ \mathrm{kpa}$ and approx $100\ \mathrm{kpa}$ is $1\ \mathrm{atm}$.


closed as off-topic by Mithoron, A.K., Todd Minehardt, Tyberius, a-cyclohexane-molecule Nov 12 '18 at 23:04

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First order rate constants are only in 1/time, i.e. the inclusion of pressure does not make any sense if it is first order.

If $X$ is a quantity proportional to the concentration then for a first order reaction $X=X_0e^{-kt}$ where $X_0$ is the amount at time zero. Hence $\ln(X/X_0) = -kt$ from which you can see that the units of $k$ are 1/time.


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