How can we determine initial rate of decomposition of H2O2 with KI catalyst usin

Question

How can we determine initial rate of decomposition of H2O2 with KI catalyst using volume of oxygen produced? I have attached a picture that shows formula (2) as the initial rate. How can we arrive to this formula in the case of H2O2 with KI, as mentioned above? 2H202(aq) - 2H20(11+02(g) Ieq2 so that the rate constant in oq 4 is applicable to any volume of reaction solution. A procedure to determine the kinetics of the iodide-catalyzed Initial Rate Measurement Based on Concentration of H,02 H,02 decomposition reaction based on water displacement from a wash bottle has been reported by Teggins and Mahaffy (I). In this procedure, the H2O2 and KI reagents totaling 300 mL are mixed and transferred to a wash bottle. As O2(g is generated, some of the reaction solution is displaced. The initial rate of reaction isdetermined by measuring the time to displace Based on H202 concentration, the initial rate is initial rate =--H202] Lab measurements will provide rotg)/(Hsolution) ×an ecific volumes. By comparing the initial rates for different runs,which will be converted to -AH O/(2Ar) as follows: e orders of reaction were both found to be 1. Compared to conventional water displacement schemes (2 3), this approach is attractive because it is easily I'(solution) >At V(solution) × [H2021 We have reported a wash bottle water displacement scheme to determine the % NaHCO3 in an Alka-Seltzer tablet, the molar mass of CO2, and the ideal gas constant R (4). Encouraged by the quality of results obtained by students, we have examinedThe temperature of the gas in the wash botde and the room the Teggins and Mahaffy (1) wash bottle water displacement atmospheric pressure (P(atm) P(O(g)) are measured so that scheme and found the following changes to be helpful: O(g) can be converted to mol O(g) according to the Reagents are added to a test tube placed in a water-filled ideal gas la wash bottle so that water is displaced instead of the reaction mol H2O2 reacted V(solution) × , Considering the equation H202-KI solution. (i) Small volumes of reagents totaling 5 mL are used. initial rate(-an201)=k[H2O2[I-r (7) 2Ar Theory nitial Rate Measurement Based on Volume of O2lg) the rate constant will have units of rate constant units = M(1-a-,-1 The initial rate is defined as The rate constant for the H2O2 decomposition is conventionally expressed according to eq 8. initial rate-V(solution) (2)

Explanation / Answer

When hydrogen peroxide is added to potassium iodide in neutral solution, the potassium iodide acts as a catalyst in the decomposition of hydrogen peroxide into water and oxygen.

The reaction occurs in two stages, via an intermediate oxyiodide (OI-) ion-

H2O2 (aq) + I- (aq) --> H2O (l) + OI- (aq)

H2O2 (aq) + OI- (aq) --> H2O (l) + O2 (g) + I- (aq)

Since the iodide ion is not consumed by the reaction, it is classed as a catalyst.

In acid solution there is a different reaction. In the presence of H+ ions, the potassium iodide is oxidised by the hydrogen peroxide into elemental iodine, and the hydrogen peroxide is reduced to water;

2KI (aq) + 2H+ (aq) + H2O2 (aq) <--> I2 (s) + 2H2O (l) + 2K+ (aq)

This reaction is reversible and therefore, unless the iodine is removed from the system, an equilibrium will be reached which will depend on temperature and the initial concentrations of the reactants.

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