The reaction 2 N 2 O 5 g → 4 N O 2 g + O 2 ( g ) follows first order kinetics. The pressure of a…

The reaction 2N2O5g→4NO2g+O2(g) follows first order kinetics. The pressure of a vessel containing only N2O5 was found to increase from 50 mm Hg to 87.5 mm Hg in 30 min. The pressure exerted by the gases after 60 min. Will be (Assume temperature remains constant) :
  1. 106.25 mm Hg
  2. 125 mm Hg
  3. 116.25 mm Hg
  4. 150 mm Hg

Solution

                 2N2O5g →4NO2g+O2g

at t=0,            P0                     0              0

at t=30 min.   (P0-x)                2x             x 2

at t=60 min.   (P0-y)                2y             y 2

∵P0=50 mmHg

∵after 30min.   ⟹ P0-x+2x+x2=87.5

P0+32x=87.5 

32x=37.5  ;  x=25mmHg

P0=50 ;  P30min=25mmHg 

That mean 30 min. is Half life of reaction. 

P0→30 min.P02→30 min.P04

at t= 60 min

PN2O5  =P04  ⟹504=12.5mmHg

P0-y=12.5 ⟹50-y=12.5

y=37.5mmHg

Total P after 60 min.  ⟹P0-y+2y+y2⟹50×32 ×37.5

=106.25 mmHg
 

Asked in: JEE Main 2015 (10 Apr Online)

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