Consider the first-order reaction AS B in which A molecules (red spheres) are converted to B molecules (blue spheres).
(a) Given the pictures at t = 0 min and t = 1 min, draw pictures that show the number of A and B molecules present at t = 2 min and t = 3 min.

Verified step by step guidance

1. Step 1: Observe the initial state at t = 0 s where all molecules are A (gray spheres).
2. Step 2: Observe the state at t = 30 s where some A molecules have been converted to B molecules (red spheres).
3. Step 3: Determine the number of A and B molecules at t = 30 s. Count the gray and red spheres.
4. Step 4: Use the observed conversion rate from t = 0 s to t = 30 s to predict the number of A and B molecules at t = 60 s (1 min).
5. Step 5: Continue using the same conversion rate to predict the number of A and B molecules at t = 90 s (1.5 min) and t = 120 s (2 min).

Key Concepts

First-Order Reaction

A first-order reaction is a type of chemical reaction where the rate is directly proportional to the concentration of one reactant. This means that as the concentration of reactant A decreases, the rate at which it converts to product B also decreases. The rate law for a first-order reaction can be expressed as rate = k[A], where k is the rate constant.

Reaction Progress Over Time

In a first-order reaction, the conversion of reactants to products occurs over time, and the concentration of reactants decreases while the concentration of products increases. The graphical representation of this process typically shows an exponential decay for reactants and an exponential growth for products. Understanding this progression is crucial for predicting the amounts of A and B at any given time.

Stoichiometry

Stoichiometry involves the calculation of reactants and products in chemical reactions based on their molar ratios. In this context, it helps determine how many molecules of A are converted to B over time. For a first-order reaction, knowing the initial concentration of A allows for the calculation of remaining A and formed B at any time, which is essential for drawing the required pictures.