Chemistry - Chemical Kinetics Question with Solution | TestHub

Methane is an important greenhouse gas since it absorbs infrared radiation. To calculate its concentration in the atmosphere, one needs to know the processes that release methane into the atmosphere and what happens to it in atmosphere.

While it is produced from a variety of natural and human-related sources, it is mainly consumed by reaction with the hydroxyl radical, which is a simple elementary reaction:

$C{H}_4{+}^{.}OH\to C{H}_3\cdot +H_{2}O$

with a rate constant equal to $4\times 10^6{M}^{-1}{s}^{-1}$.

It is also known that in the atmosphere, ${}^{.}OH$ radicals are constantly produced and removed, so their concentration is approximately constant and is equal to $1\times 10^{-15}M$. Similar to methane, isoprene is also released in significant amounts and has absorbing power. It is also removed in a similar manner with a rate constant equal to $2\times 10^{11}{M}^{-1}{s}^{-1}$.

Also, the average lifetime of a reactant following first-order kinetics is $t_{avg}=1/K$. Using this information, answer the questions that follow.