Wash Bottle Laboratory Exercises: Iodide-Catalyzed H₂O₂ Decomposition Reaction Kinetics Using the Initial Rate Approach

Abstract

The catalyzed H 2 O 2 decomposition reaction is 2H 2 O 2 ðaqÞ sf catalyst 2H 2 OðlÞ þ O 2 ðgÞ (1Þ A procedure to determine the kinetics of the iodide-catalyzed H 2 O 2 decomposition reaction based on water displacement from a wash bottle has been reported by Teggins and Mahaffy (1). In this procedure, the H 2 O 2 and KI reagents totaling 300 mL are mixed and transferred to a wash bottle. As O 2 (g) is generated, some of the reaction solution is displaced. The initial rate of reaction is determined by measuring the time to displace specific volumes. By comparing the initial rates for different runs, the 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 performed. We have reported a wash bottle water displacement scheme to determine the % NaHCO 3 in an Alka-Seltzer tablet, the molar mass of CO 2 , and the ideal gas constant R (4). Encouraged by the quality of results obtained by students, we have examined the Teggins and Mahaffy (1) wash bottle water displacement scheme and found the following changes to be helpful: (i) Reagents are added to a test tube placed in a water-filled wash bottle so that water is displaced instead of the reaction H 2 O 2 -KI solution. (ii) Small volumes of reagents totaling 5 mL are used. Theory Initial Rate Measurement Based on Volume of O 2 (g)The initial rate is defined asis the volume of the reaction solution in liters (L), and Δt is the displaced water collection time in seconds (s). Considering the equationwhere k is the rate constant, h is the order with respect to H 2 O 2 , and i is the order with respect to I -, the rate constant will have units ofIt is essential to include V(solution) in the definition of initial rate in eq 2 so that the rate constant in eq 4 is applicable to any volume of reaction solution. Initial Rate Measurement Based on Concentration of H 2 O 2Based on H 2 O 2 concentration, the initial rate isThe temperature of the gas in the wash bottle and the room atmospheric pressure (P(atm) = P(O 2 (g)) are measured so that the V(O 2 (g)) can be converted to mol O 2 (g) according to the ideal gas law. Considering the equation initial rate -Δ½H 2 O 2 2Δt ¼ k½H 2 O 2 h ½I -i (7Þ the rate constant will have units of rate constant units ¼ M ð1 -h -iÞ s -1 (8Þ The rate constant for the H 2 O 2 decomposition is conventionally expressed according to eq 8. Order of Reaction with Respect to H 2 O 2 With [I -] fixed and the [H 2 O 2 ] varied from one run to another initial rate ¼ -Δ½H 2 O 2 2Δt ¼ k½I -i ½H 2 O 2 h ¼ k 0 ½H 2 O 2 h (9Þ where k 0 ¼ k½I -i (10Þ The order of the reaction with respect to [H 2 O 2 ] can be

Mathematical modelling in high school chemistry: Chemical kinetics

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Experiment Optimization on the Reaction Rate Determination and Its Implementation in Chemistry Learning to Develop Science Process Skills

“…Practicum of gas formation, such as hydrogen peroxide decomposition, can be used in reaction rate learning because it can demonstrate the concept of reaction rates quantitatively (Cybulskis et al, 2016). This practicum can demonstrate the fundamental concepts, including the peroxide reaction rate (Barlag, 2010), reaction enthalpy (Tatsuoka and Koga, 2013), activation energy (Sweeney et al, 2014) and has relevance to various other sciences (Cybulskis et al, 2016).…”

“…The use of hypotheses is done by plotting the reaction rate (y-axis) with [H2O2] (x-axis), if it is proven to be linear, it can be said that the reaction is first order. To test whether the reaction is second order, it is done by plotting the reaction rate (y-axis) with [H2O2] 2 (x-axis) (Barlag, 2010). To find out the linearity of a graph, a Microsoft Excel application can be used.…”

Kinetics of hydrogen peroxide decomposition catalyzed by Cu‐buserite over a well‐sealed and thermostated kinetics assembly

“…In order to gain a deeper insight into the kinetic concepts, rate constant, reaction order, and rate law, etc., the decomposition of H 2 O 2 prompted by some catalysts, for example, yeast, 15 catalase, 16 iodide, 17–20 metals, 21,22 and inorganic oxides, 22–27 has been performed in chemistry kinetics study. Buserite‐type manganese oxides (Me‐buserite) possesses a two‐dimensional layered structure, which forms MnO 2 sheets of edge‐sharing MnO 6 octahedra assembled in layers and two sheets of water molecules and metal cations in the interlayer region.…”

“…In the kinetic studies of H 2 O 2 decomposition, the kinetic data needed for the linear least‐squares fitting are commonly acquired through measuring the O 2 production 15–21 by the so‐called volumetric or manometric method or H 2 O 2 concentration 22–27 by the Ghormley triiodide method as a function of time. In the Ghormley triiodide method, the absorbance of I 3 − , the oxidized product of I − , is measured spectrophotometrically at a wavelength of 355 nm after extracting and filtering the sample 22 .…”