100 grams Helium Gas are in a sealed container at STP. How many grams are there?

100 grams,

Explanation:

Note: I assume you want to find the volume of the gas, since the mass (100 grams) is already given.

First of all, we have to find the number of moles of the gas. This is given by:

where

m = 100 g is the mass of the gas

is the molar mass of helium

Substituting,

Now we have to find the volume of the gas. We can do it by using the equation of state for an ideal gas:

where

is the pressure of the gas at STP

V is the volume of the gas

n = 25 mol is the number of moles

is the gas constant

is the temperature at STP

Solving for V, we find the volume: