Dinitrogen difluoride gas is collected at $33\mathrm{.}0$ degrees C in an evacuated flask with a measured volume of $20\mathrm{.}0$ L$.$ When all the gas has been collected, the pressure in the flask is measured to be $0\mathrm{.}150$ 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.