Physics
posted by Sean .
A sample of helium behaves as an ideal gas as it is heated at constant pressure from 273 K to 353 K. If 25.0 J of work is done by the gas during this process, what is the mass of helium present?

Work = P *(V2  V1) = 25.0 J
Now, since V = nRT/P where n is the number of moles of He, pressure cancels out and
W = n*R*(T2  T1)
R is the gas constsnt.Solve for n, the number of moles. That and the atomic mass of He (4.00) will tell you the mass. 
R = 8.3145 J/mol K in case you need that number to solve for n

.096 kg