# Section 1 Harcourt-Essen Reaction

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A2 Chemistry Coursework Section 1 Aims: I aim to find out the order of reaction with respect to [H2O2] and [2I-]. I aim to find out the activation enthalpy of the reaction by finding the rate of reaction at different temperatures using the Arrhenius Equation. The experiment will go as follows: Into a conical flask put 15cm3 of distilled water and add 2cm3 of [X]moldm-3 potassium iodide (KI) solution and 1cm3 of 2moldm-3 sulphuric acid. Then add to this 2.5cm3 of 5vol (0.42moldm-3) hydrogen peroxide (H2O2). For the second part of my investigation, the KI solution will remain a constant 0.3moldm-3 and the H2O2 solution will vary. H2O2 + 2I- + 2H+ -> 2H2O + I2 Methods to find the rate: 1 - Use a colorimeter to monitor the change…show more content…
Transmittance can be expressed as the ratio of the intensity of the transmitted light (It) and the initial intensity of the light beam (Io), as expressed by the formula: reference 4 T = It /Io Experimental Methods: Making up the solutions: The potassium iodide solution will be made up by first calculating the amount (in moles) of KI needed from the equation: concentration = amount/volume as I know the desired concentration(s) and how large a volume I want to make up. Then I can calculate how exactly how much solid KI (in grams) is needed for that concentration by using the equation: amount = mass/Mr - given the Mr of KI is 166.0028. Then to actually make up the solution, I will first brush the balance, place a plastic weighing container on it, and then tare the balance. I will then proceed to accurately weigh out the required mass of KI with a clean spatula. The hydrogen peroxide solution will be diluted from 20vol to [X]vol by using 20/[X] the volume of 20vol H2O2 in distilled water. Methods: Potassium iodide solution: 1. Using the equations; amount = mass/Mr and concentration = amount/volume, I calculated the correct mass of KI needed to make up the required concentrations of KI solution (0.05 through to 0.3moldm-3). I used the complete values throughout all the equations, and then rounded my final volume to an appropriate decimal place relative to the precision of the scientific balance I will use to make up the solution. 2. Solid KI (mass m) was weighed