Final answer:
The rate of change of ClF₃ is determined by calculating the rate of decrease of F₂ and then using the mole ratio from the reaction to find the formation rate of ClF₃, which is 0.00378 M/s over 15 seconds.
Step-by-step explanation:
To determine the rate of change of ClF₃ in the reaction Cl₂(g) + 3F₂(g) → 2ClF₃(g), you need to consider the stoichiometry of the reaction and the change in concentration of F₂ over time. If F₂ decreases from 0.950 M to 0.865 M over 15 seconds, the change in concentration (Δ[F₂]) is 0.950 M - 0.865 M = 0.085 M. Since 3 moles of F₂ react to produce 2 moles of ClF₃, the rate of formation of ClF₃ will be (2/3) times the rate of decrease of F₂.
First, calculate the rate of decrease of F₂: Rate = Δ[F₂] / Δt = 0.085 M / 15 s = 0.00567 M/s. Next, find the rate of formation of ClF₃: Rate(ClF₃) = (2/3) × Rate(F₂) = (2/3) × 0.00567 M/s = 0.00378 M/s. This is the average rate of change of ClF₃ concentration during the 15-second interval.