Chemistry
posted by naseeb .
A 1.50mol sample of helium at a certain temperature and pressure has a volume of 31.4L. A second sample of helium at the same temp and pressure has a volume of 42.2L. How many moles of Helium are in the second sample?

well, PV=nRT so
V/n=RT/P so if RT/P remains constant
V1/n1=V2/n2
and you are solving for n2.