I am not a chemist. I hope I will be specific enough.
Suppose there are two chemical species $\ce{A}$, $\ce{B}$ with the following properties:
- at temperature $t < T_r$, no reaction occurs between $\ce{A}$ and $\ce{B}$ (in any combination).
- at $t\ge T_r$, $\ce{A}$ interacts with itself to create $\ce{A_2}$, $\ce{B}$ reacts with itself to create $\ce{B_2}$, and $\ce{A}$ and $\ce{B}$ are reacting to create $\ce{AB}$.
- $\ce{A_2}$, $\ce{B_2}$ and $\ce{AB}$ are never reacting.
In experiment, we first mix $\ce{A}$ and $\ce{B}$ in temperature $t<T_r$. Amounts of species mixed are $a$ for $\ce{A}$, $b$ for $\ce{B}$. Then, we add heat to obtain temperature $t\ge T_r$ and start the reaction.
- What amounts of $\ce{A_2}$, $\ce{B_2}$, and $\ce{AB}$ can be expected to be produced?
- To obtain the amounts, should probability theory be used? E.g., amount of $\ce{AB}$ equals to probability that species $\ce{A}$, $\ce{B}$ will interact ("collide" or similar interpretation).
Assume the rates of the reactions are equal.