Fasten a piece of aluminum foil over the opening of a clean 125 mL Erlenmeyer flask. Make a tiny hole in the conter of the foil with a pin. WEIGH THE DRY FLASK with foil cap/ Secure about 3 mL of unknown liquid and pour it into the flask, replacing with the foil cap. Record the number of the unknown (REWEIGHING IS NOT NECESSARY). As it boils away, the vapor of the unknown pushes the aire out of the flask through a tiny pinhole opening, and eventually the flask is filled witha an atmosphere composed exlcusively of the unknown. The P, V, and T of the vapor will be determined and number of moles will be c alculated. When the flask is allowed to cool the vapor condenses and aire again refulls the flask. Re weighing the flask and figure out the the wight of the unknown vapor which filled the flask during the boiling.
Q: Explain why it is not necessary to know the weight of the unknown liquid placed in the flask.