The decomposition of hydrogen peroxide in the presence of potassium iodide is believed to occur by the following mechanism:
step 1 slow: H2O2 + I^- = H2O + OI^-
step 2 fast: H2O2 + OI^- = H2O + O2 + I^-
1) What is the equation for the overall reaction? Use the smallest integer coefficients possible.
I am not sure about this part.
2) Which species acts as a catalyst? Enter formula if there is one.
I think that I^- is the catalyst.
3) Which species acts as a reaction intermediate?
I think the H2O2 is the reaction intermediate.
4) Complete the rate law fot the overall reaction that is consistent with this mechanism.
I know that it would be k[][] but I am not sure what it is.
Thank you for your help!!
1) To determine the overall reaction, we need to cancel out the common species on both sides of the equations. Looking at the two given steps:
Step 1: H2O2 + I^- = H2O + OI^-
Step 2: H2O2 + OI^- = H2O + O2 + I^-
By adding these two steps, we can cancel out H2O2 on both sides:
H2O2 + I^- + H2O2 + OI^- = H2O + OI^- + H2O + O2 + I^-
2H2O2 + I^- + OI^- = 2H2O + OI^- + O2 + I^-
Simplifying, we can cancel out I^- and OI^- on both sides:
2H2O2 = 2H2O + O2
Therefore, the overall reaction is: 2H2O2 → 2H2O + O2
2) Based on the given mechanism, the species I^- acts as a catalyst. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.
3) Reaction intermediates are species that are formed in one step of a reaction mechanism and consumed in a subsequent step. In this case, neither H2O2 nor any other species is formed in one step and consumed in the subsequent step. Therefore, there is no reaction intermediate in this mechanism.
4) The rate law for the overall reaction is determined by the rate-determining step, which is typically the slowest step in the mechanism. In this case, step 1 is the slow step.
From step 1: H2O2 + I^- → H2O + OI^-
The rate law for this step can be given as:
rate = k[H2O2][I^-]
Since step 1 is the slow step and the overall reaction rate is determined by this step, the rate law for the overall reaction can be expressed as:
rate = k[H2O2][I^-]
Note that the rate law may differ if there are other elementary steps involved in the reaction. However, based on the given mechanism, this is the rate law for the overall reaction.