1. Question Statement and details : 500 mL of 56V H2O2 is kept in an open container due to which some H2O2 is decomposed and evolves 8gm O2 simultaneously, during the process some H2O also vapourizes.Due to all these changes final volume is reduced by 20%. Find final volume strength of H2O2 (aq). It's a multiple choice question. Options are as follows (a.) 56V (b) 44.8 V (c.) 11.2V (d.) 33.6V. Correct Answer is 33.6 V. 2. Relevant Equations: Molarity = Volume strength/11.2 and Normality = Volume Strength , in balanced reaction 1 mol H2O2 gives 1/2 half mol O2. Mol. Wt. H2O2=34. 3. The attempt at a solution : By stoichiometry 1/2 moles of H2O2 gives 1/4 moles of O2. So volume strength of H2O2 used to give 8gm is 22.4*1/4 = 5.6. So I subtracted that from 56V. And then simply reduced what i got by 20% it didn't work though. What i'm getting is 39.6 not close to the answer which is 33.6 V. Please help me out on this one. Thank You.