Question

Decomposition of H2O2 follows a first order reaction.In 50 minutes the concentration of H2O2 decreases from 0.5 to 0.125 M in one such decomposition.When the concentration of H2O2 reaches 0.05M, the rate of formation of O2 will be

Answer 1

We first write the equation for the compound. The compound in question is hydrogen peroxide.

2 H₂O₂ (l) —> 2 H₂O (l) + O₂ (l)

The mole ratio is 2 : 1

That is : for every two moles of hydrogen peroxide decomposing 1 mole of oxygen is formed.

From the information given above we can get the rate of decomposition of hydrogen peroxide from :

0.5 moles to 0.125 moles in 50 minutes.

0.5 - 0.125 = 0.375 moles.

0.375 / 50 = 0.0075 moles per minute.

When the hydrogen peroxide reaches 0.05 moles, we can get the time it takes to reach 0.05 moles from the rate.

0.125 - 0.05 = 0.075 moles.

Time = 0.075 / 0.0075 = 10 minutes


Thus in 10 minutes the moles of hydrogen peroxide change from 0.125 moles to 0.05 moles.


From the mole ratio :

The moles of oxygen when hydrogen peroxide Is 0.05 moles is :

0.05 / 2 = 0.025 moles

When hydrogen peroxide is 0.125 moles :

0.125 / 2 = 0.0625 moles

The change in moles after 10 minutes for oxygen is :

0.0625 - 0.025 = 0.0375 moles.

The rate of formation of oxygen is thus :

0.0375 / 10 = 0.00375 moles per minute.


Answer :

0.00375 moles per minute.