The highest vacuum attained so far is of the order of 10-11 mm of Hg. How many molecules are there in 1m3 of a vessel under such a high vacuum at 0ºC ?
3.5×1014
6.4×1017
6.4×1027
2.2×1012
PV=nRT=NNART=NkT⇒N=PVkT=10−11(13000)(9.8)(1)1.38×10−23(273)=3.5×1014