posted by Anna .
What mass of Helium will occupy 2 times the volume of 10.0 grams of Neon if both gases are measured at STP?
The long way of doing this is to use PV = nRT, make up a P and T and solve for volume of 10.0 g Ne and multiply that by 2. [n Ne = grams/molar mass.] Then use PV = nRT again, same P and T, substitute 2xV for Ne and solve for n He, than convert to grams He.
Short way is V = n*k