A closed vessel with rigid walls contains 1mole of 23892U and 1 mole of air at 298 K. Considering complete decay of 23892U to 20682Pb, the ratio of the final pressure to the initial pressure of the system at 298 K is
23892U → 20682Pb+8 42He(g)+6 ∘−1β
n(gas) [Initial] = 1 (air)
n(gas) [Final] = 8(He) + 1(air) = 9
⇒ At constant temperature and volume
p∝n
So, pfti=nfni=91=9