Final answer:
The average rate of the given reaction over the first 13.0 seconds is found by calculating the change in concentration of I⁻ per unit of time, which is 0.01215 M/s.
Step-by-step explanation:
The student has presented a balanced chemical equation: H₂O₂(aq) + 3I⁻(aq) + 2H⁻⁺(aq) → I₃⁻(aq) + 2H₂O(l) and has provided initial and final concentrations of I⁻ to calculate the average rate of reaction within a given time frame. To find the average rate, we can use the change in concentration of I⁻ over the time interval. Since the concentration of I⁻ dropped from 1.000 M to 0.842 M in the first 13.0 seconds, we can calculate the rate as follows:
Average rate = change in concentration of I⁻ / change in time = (0.842 M - 1.000 M) / 13.0 s = -0.158 M / 13.0 s = -0.01215 M/s
The negative sign indicates the disappearance of the I⁻ over time, but we typically report rates as positive numbers, hence the average rate of reaction is 0.01215 M/s. Keep in mind that this rate is specific to the disappearance of I⁻, but could be adjusted for other species by considering their stoichiometry in the balanced equation.