Following the instructions in the lab, remembering that 1000 g is 1 L of water,
ID: 773048 • Letter: F
Question
Following the instructions in the lab, remembering that 1000 g is 1 L of water, what is the %w/w of hydrogen peroxide if the volume of a 0.01595 M KMnO4 was 15.14 to tritrate the sample?Explanation / Answer
The reactions followed are : 2MnO4-(aq) + 6H+ (aq) + 5H2O2(aq)-----> 5O2(g) + 8H2O(l) + 2Mn2+(aq) in acidic medium. 2MnO4-(aq) + 2H+ (aq) + 3H2O2(aq)-------> 3O2(g) + 4H2O(l) + 2MnO2(s) in basic medium The stoichiometric ratio of MnO4- and H2O2 is 2:5 and 2:3 respectively. case 1 : ratio =2:5 (acidic medium) No of mmol of KMnO4 = (0.01595*15.14)= 0.24148 mmol No of mmol of H2O2 = (0.24148*5)/2 mmol =0.6037 mmol .wt =0.6037*34 =20.526 g so % wt of H2O2 = (20.526/ mass of H2O2) *100 =(20.526/volume of H2O2 * density) *100 case 2 : ratio =2:3 (basic medium) No of mmol of KMnO4 = (0.01595*15.14)= 0.24148 mmol No of mmol of H2O2 = (0.24148*3)/2 mmol =0.3622 mmol .wt =0.3622*34 =12.315 g so % wt of H2O2 = (12.315/ mass of H2O2) *100 = (12.315/volume of H2O2 * density) *100 The eaxact value of wt% can be calculated by knowing the volume of H2O2 used in the solution.