Post Lab Question 2

Question

The decomposition of hydrogen peroxide in dilute sodium hydroxide at 20 °C is first order in H₂O₂.

H₂O₂(aq)H₂O(l) + ½ O₂(g)

During one experiment it was found that the H₂O₂ concentration dropped from 6.50×10^-2 M at the beginning of the experiment to 2.41×10^-2 M in 806 min. What is the value of the rate constant for the reaction at this temperature?  min^-1

Answer 1

For a first order reaction, we can write the integrated rate law as

[A] = [A]_oe^-kt

ln [A] = -kt + ln [A]_o

ln (2.41x10^-2 M) = - k(806 min) + ln (6.50x10^-2 M)

-3.726 = -806 k - 2.733

-0.993 = -806 k

k = 1.23x10^-3 min^-1