See image — AITS & Test Series Chemistry Question

💡 Solution & Explanation

Let the no. of moles of H2, O2 and He are x, y and z respectively x + y + z = 2.0 Pressure exerted by 2 moles of gaseous mixture is 50 atm. After the first electric spark decrease in pressure = 50 – 12.5 = 37.5 atm decrease in no. of moles of gaseous mixture is 1.5 But from the given information limiting reagent in first step is O2 from    2 2 2 1 H g O g H O 2    H2 and O2 reacted are in the ratio of 2 : 1 0.5 mole of O2 should be reacted with 1.0 mole of H2 No. of mole of O2 in the mixture (y) = 0.5 When again O2 is passed, pressure increased from 12.5 to 25.0 atm Change in pressure = 12.5 atm No. of moles of O2 added = 12.5 2