Question

The decomposition of hydrogen peroxide is first order in H₂O₂. 2H₂O₂ → 2H₂O + O₂ The rate constant for this reaction at 20 C is 1.8 x 10⁻⁵ s⁻¹. If the starting concentration of H₂O₂ is 0.75 M, determine (A) the concentration of H₂O₂ remaining after 3 hours and (B) How long it will take for the H₂O₂ concentration to drop to 0.10 M?

Answer 1

To determine the concentration of H2O2 remaining after 3 hours and how long it will take for the H2O2 concentration to drop to 0.10 M, we can use the first-order rate equation for the reaction.

Step-by-step explanation:

To determine the concentration of H2O2 remaining after 3 hours, we can use the first-order rate equation for the reaction. The rate constant (k) is given as 1.8 x 10⁻⁵ s⁻¹. We can use the formula: ln([H2O2]t/[H2O2]0) = -kt, where [H2O2]t is the concentration at time t, [H2O2]0 is the initial concentration, k is the rate constant, and t is the time.

For part A, we have [H2O2]0 = 0.75 M and t = 3 hours. Plugging these values into the formula, we get: ln([H2O2]t/0.75) = -(1.8 x 10⁻⁵ s⁻¹)(3 hours x 60 minutes/hour x 60 seconds/minute). Solving for [H2O2]t gives us the concentration of H2O2 remaining after 3 hours.

For part B, we need to determine the time it takes for the H2O2 concentration to drop to 0.10 M. We can rearrange the first-order rate equation to solve for t: t = ln([H2O2]t/[H2O2]0)/(-k). Plugging in [H2O2]t = 0.10 M, [H2O2]0 = 0.75 M, and the given value of k, we can solve for t.