A student investigates the catalytic decomposition of aqueous hydrogen peroxide at 25 °C according to the overall reaction
2 H₂O₂(aq) → 2 H₂O(l) + O₂(g)
During one 30 s interval she measures the concentration of H₂O₂ to decrease from 0.400 mol L⁻¹ to 0.352 mol L⁻¹.
(a) Describe, in words, what is meant by the "average rate of disappearance of H₂O₂" over this 30 s interval.
(b) Using the balanced equation, explain why the magnitude of the average rate of appearance of O₂ is one-half the magnitude of the average rate of disappearance of H₂O₂.
(c) Identify the appropriate SI units for (i) the average rate of disappearance of H₂O₂ and (ii) the average rate of appearance of O₂ for this experiment. Justify your choices.
(d) If the student reported the rate of disappearance of H₂O₂ as −1.6 × 10⁻³ mol L⁻¹ s⁻¹, discuss whether the negative sign is appropriate and interpret its physical meaning in the context of this reaction.