Question

21. Hydrogen peroxide in solution decomposes to give water and oxygen gas. From the
following data show that decomposition of H2O2 in aqueous solution is a first-order
reaction.
time (min) 0,15,30

Vol (mL) of KMnO4 25.4 ,9.83, 3.81

The volume of standard KMnO4 is given for titrating the same volume of the reac-
tion mixture.​

Answer 1

Answer:

Given that decomposition of H

2

O

2

in aqueous solution follows first order kinetics.

For first order reactions,

K=

t

1

ln

[A]

t

[A]

0

where, K is the rate constant,

t= time

[A]

0

= Initial concentration of reactant (i.e. H

2

O

2

)

[A]

t

= concentration of reactant at t=t

Now, concentration of H

2

O

2

present at any time is proportional to volume of KMnO

4

used in titration.

Now, given that

at, t=0; volume of KMnO

4

used=22.8mL∝[A]

At t=600s;Volume of KMnO

4

used=13.8mL∝[A]

t

So, K=

600

1

ln(

13.8

22.8

)

⇒K=

600

1

×0.5=0.00084s

−1