JEE Main 2015ChemistryChemical KineticsMediumMCQ

JEE Main 2015 — Chemical Kinetics Question with Solution

JEE Main 2015 (10 Apr Online)

Question

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) :

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Show full solutionCorrect option: A
Correct answer
A106.25 mm Hg

Step-by-step explanation

                 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
 

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About this question

This is a previous-year question from JEE Main 2015, covering the Chemical Kinetics chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.