JEE Main levelSingle correct optionDifficulty 2 of 3mc098
NX2OX4 (92g/mol) partly dissociates as NX2OX42NOX2 at a certain temperature, and the equilibrium mixture has vapour density 34.5. The degree of dissociation of NX2OX4 is
A25.0%
B33.3%
C16.7%
D75.0%
Answer: B
Initial vapour density D = 92/2 = 46. For 1 mol dissociating by α, moles = 1 + α, and mass is conserved, so d = D/(1+α). α = (D - d)/d = (46 - 34.5)/34.5 = 0.3333 = 33.3%.