Parallel Reaction: [C]/[D]=k1/k2 at t=0,t=t

Introduction:
In chemistry, parallel reactions are those in which a single reactant is converted into multiple products via different pathways. The rate of each reaction is determined by its own rate constant, and the overall rate of the reaction is determined by the slowest step.

Equation:
For a parallel reaction, the ratio of concentrations of products C and D at any given time t can be expressed as [C]/[D] = k1/k2. This equation holds true at both t=0 and t=t, where t=0 represents the initial state of the reaction and t=t represents the final state of the reaction.

Explanation:
The ratio of concentrations of products C and D is given by the ratio of their respective rate constants k1 and k2. This means that the rate of formation of C is directly proportional to k1 and the rate of formation of D is directly proportional to k2. At t=0, the reaction has just started and the initial concentration of both products is zero. As the reaction proceeds, the concentration of both products increases, but their ratio remains constant at k1/k2.

Interpretation:
The ratio of product concentrations [C]/[D] is a measure of the selectivity of the reaction towards each product. If the ratio is close to 1, it means that the reaction is equally likely to form both products. If the ratio is much greater than 1, it means that the reaction is highly selective towards one product over the other.

In conclusion, the ratio of concentrations of products C and D in a parallel reaction is determined by the ratio of their respective rate constants k1 and k2. This ratio remains constant throughout the reaction, from t=0 to t=t. The ratio is a measure of the selectivity of the reaction towards each product.