Rate question of decomposition

Question

Decomposition of H2O2 was observed for several days. Initially the H2O2 was present at 0.50mol L-1 after 2 days the H2O2 was 0.25mol L-1 what is the rate of this reaction

Answer 1

2 H₂O₂ → 2 H₂O + O₂

rate = - Δ Concentration / Δ time

A negative sign is included in the above equation to ensure the rate of the reaction equals a positive number. This is because the change in the concentration of H₂O₂ (reactant) is negative as it is decreasing over time.

= - (C₂ - C₁) / t₂ - t₁

= - (0.25 - 0.50) / (2 - 0)

= 0.25 / 2 = 0.125 mol L^-1 day^-1 (or 0.125 M day^-1)