At 300 K a gaseous reaction A rarr B +Cwas found to follow first order kinetics . Starting with pure A the total pressure at the end of 20 minutes was 100 mm of Hg . The total pressure after the completion of the reactionn is 180 mm of Hg .The partial pressure of A ( in mm of Hg ) is :

At 300 K a gaseous reaction A rarr B +Cwas found to follow first order

1.	At 300 K a gaseous reaction A rarr B +Cwas found to follow first order kinetics . Starting with pure A the total pressure at the end of 20 minutes was 100 mm of Hg . The total pressure after the completion of the reactionn is 180 mm of Hg .The partial pressure of A ( in mm of Hg ) is :
Answer» 100 90 180 80 Solution :`A to B + C` On decomposition of 1 mole of A , 1 mole of B and 1 mole of C are PRODUCED . THUS the total pressure after completion of the reaction corresponds to 2 MOLES and initial pressure to 1 mole . Initial pressure of A , (i.e, `p_(0) = (1)/(2) xx 180 = 90` MM Hg .... (1) `{:(, A to ""B + C) , ("at t = 0" , p_(0) ""0 ""0) , ("after 20 min" , p_(0)-p""p "" p):}` After 20 minutes , the total pressure = 100 mm Hg . `p_(0) - p + p + p = 100` `p + p = 100` from equation (1) `90 + p = 100` `p = (100 - 90) = 10`mm Hg So partial pressure of `A = p_(0) - p` `= 90 - 10 = 80` mm Hg.