# Finding the Rate Equation

520 Words3 Pages
Date: February 15, 2013 Title: The Iodine Clock Reaction Aim: i. To determine the order of the reaction between sodium peroxodisulphate (VII) and potassium iodide from initial rates ii. To determine the rate law of the reaction between sodium peroxodisulphate (VII) and potassium iodide. Theory: Define rate equation, rate constant, and the order of a reaction with respect to a particular reagent, describing methods of finding the order. Define also the overall order of a reaction and describe how it’s found. Explain how the iodine clock reaction works and the method it employs to find the order of a reaction with respect to a particular reactant. Experimental: Apparatus: 3 -100 cm3 beakers, 1 thermometer, 0-100 0C, 8 burettes with beakers and funnel for filling, clamps and stands, stop clock or watch. Reagents: Potassium peroxodisulphate (VI) solution [0.100 mol dm-3 and 0.050 mol dm-3 K2S2 O8], Potassium iodide solution, [0.500, mol dm-3 and 0.250 moldm-3, KI], Sodium thiosulphate solution, [0.010 mol dm-3 Na2S2O3], Starch solution, 0.2% Procedure: 1. Using a burette, run 5.0 cm3 of 0.100 mol dm-3 peroxodisulphate solution into a 100 cm3 beaker. Add 45 cm3 of distilled water, from a burette, stir gently to mix. 2. Using burettes, measure out 15 cm3 of each of the 0.500 mol dm-3 potassium iodide, 3 cm3 of 0.010 mol dm-3 sodium thiosulphate solutions and 2.0 cm3 of starch solution into the second 100 cm3 beaker. 3. Measure the temperature of the two solutions. Pour the contents of the second beaker into the first, immediately start the clock and shake to mix. 4. When the blue colour of the starch-iodine complex appears, stop the clock and write down the time in the Results Table. 5. Repeat the experiment using the concentrations outlined below: Test | Concentration of Reagents/ mol dm-3 | | [Na2S2O8] | [KI] | 1 | 0.10 |