The decomposition of hydrogen peroxide to water and oxygen is a first order reaction with a rate constant of 0.0410 min^{- 1}. If we start with 0.500 M H₂O₂, what will be its concentration after 10.0 minutes?

Question

Quizplus · Accepted Answer

The rate law for the decomposition of hydrogen peroxide is given as:
rate = k[H2O2]
where k is the rate constant.

Since it is a first-order reaction, we can use the integrated rate law to calculate the concentration of H2O2 after 10 minutes:
ln[H2O2] = -kt + ln[H2O2]0
where [H2O2]0 is the initial concentration of H2O2

ln[H2O2] = -(0.0410 min^-1)(10.0 min) + ln(0.500 M) = -0.303

[H2O2] = e^-0.303 = 0.737 M

Therefore, the concentration of H2O2 after 10 minutes is 0.737 M. However, the question asks for the concentration of H2O2, not the reactant.

Since the reaction is stoichiometrically balanced, the concentration of H2O2 is reduced by a factor of 2 for every mole of O2 produced. Thus, the concentration of H2O2 after 10 minutes is:

[H2O2] = (0.500 M) / 2 = 0.250 M

Therefore, the best choice is C (0.332 M is incorrect because it is higher than the initial concentration).

The Decomposition of Hydrogen Peroxide to Water and Oxygen Is