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# The equilibrium constant Kp for the reactionN2O4(g)⇌2NO2(g) is 4.5What would be the average molar mass (in g/mol) of an equilibrium mixture of N2O4 and NO2 formed by the dissociation of pure N2O4 at a total pressure of 2 atm?

A
69
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B
57.5
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C
80.5
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D
85.5
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Solution

## The correct option is B 57.5Let initial mole of N2O4(g) is one N2O4(g)⇌2NO2(g)initial moles 10At equilibrium1−α2xTotal number of moles at equilibrium =1+αPN2O4=1−α1+α×PPNO2=2α(1+α)×PHence,KP=P2NO2PN2O4=4α2(1−α2)×2∴4.5=4α2(1−α2)×2⇒α=0.6Mole fraction of N2O4:XN2O4=1−α1+α=0.25∴XNO2=0.75Average molar mass of mixture=0.25×92+0.75×46=57.5  Suggest Corrections  0      Similar questions  Related Videos   Archimedes' Principle
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