Dinitrogen difluoride gas is collected at -17.0 degree C in an evacuated flask with a measured volume of 30.0 L. When all the gas has been collected, the pressure in the flask is measured to be 0.260 atm. Calculate the mass and number of moles of dinitrogen difluoride gas that were collected. Be sure your answer has the correct number of significant digits. mass: g mole: mol