[jdziegler]

A neon sign is made of glass tubing whose inside diameter is 2.0 cm and length of 4.0 m. If the sign contains neon at a pressure of 1.5 torr at temperature of 35C, how many grams of neon are in the sign?

[Perito]

Neon is one of the inert gases. It is essentially one of the "ideal gases".

PV = nRT where
P = pressure
V = Volume
T = Absolute temperature (usually in Kelvins)
n = the number of moles of gas
R = the universal gas constant

You can find values of the universal gas constant here:

Gas constant - Wikipedia, the free encyclopedia

Be sure and pick out the one that is consistent with the units you are using.

Your problem is to figure out the internal volume of the tubing. You already know its pressure, 1.5 torr, and its temperature, ((273.15 + 35) kelvins). You solve for n, the number of moles. Once you have the number of moles, simply multiply by the atomic weight of neon in g/mole (mole * g/mole = g).