1. The problem statement, all variables and given/known data Blimps are being considered for use as freight carriers. A scale model rises when filled with helium to a volume of 55.0 dm3. When 1.10 mol He is added to the blimp, the volume is 26.2 dm3. How many more grams of He must be added to make it rise? Assume constant T and P. (4.003 g He = 1 mol He) 2. Relevant equations PV = nRT R = 0.8206 ( litres-atm/mole-K ) 1 dm^3 = 1L 3. The attempt at a solution Required volume to fill is 28.8 dm^3 or L PV = nRT Assume T and P is constant? How do we do that? That is my question.