Question

By thermometric titration of a hypochlorite solution with a solution of propanone you will find the equivalent amounts of the reactants and consequently, the reaction products. Procedure: For the reaction of a hypochlorite solution with a propanone use solutions tempered at laboratory temperature (check).Put 100,0cm³ of a hypochlorite solution into a thermobeaker, insert a thermometer and keep adding a 4-molar solution of propanone in 1,0cm³ portions from burette, stirring the reaction mixture continuously by means of the thermometer (carefully, do not break!). Stir the reaction mixture thoroughly after each addition and read the highest temperature reached. Keep on adding the propanone solution as long as the temperature rises. Then add three more portions and finish the experiment. Keep the reaction mixture for possible later use. 

1. Write equation for the chemical reaction and name the product that is formed. 

2. Suggest a calculation for the approximate value of the reaction heat from the data obtained. 

3. Consider the procedure of isolation of the product from the reaction mixture and give the method of its identification. 

4. The exact concentration of a hypochlorite solution can also by determined by measuring the volume of oxygen released after catalytic decomposition of hypochlorite. Illustrate the principle of this method by means of a chemical equation and show schematically the procedure for the calculation. 

Answer 1

1. CH₃COCH₃ + 3ClO⁻→ CHCl₃ + 2OH⁻+CH₃COO⁻ chloroform

2. Calculation of heat evolved in the course of the reaction: 

Q =m c∆t 

Q –reaction heat, 

m –mass of the solution, 

c –specific heat capacity of the solutions taking part in the reaction, 

∆t –temperature difference (elevation of temperature) On the basis of the data obtained in the task, it is possible to calculate Q value per one mole of reactant. 

3. The mixture contains: reactants – (excess of about 3cm³ of the 4-molar propanone solution), products – CHCl₃,OH−,CH₃COO⁻.Acetone and chloroform are separated from other substances in the aqueous solution by means of a separatory funnel and a subsequent distillation. Identification of chloroform: smell, density. 

4. 2ClO⁻ → O₂

2 mol →1 mol = 22.4 dm³