Final answer:
The molar mass of a volatile liquid can be determined by heating it to convert it into a gas and applying the concept of molar volume at STP, which is 22.4 L/mol. For a substance with a vapor density of 1.783 g/L at STP, the molar mass is calculated as 1.783 g/L multiplied by 22.4 L/mol, resulting in a molar mass of 39.9 g/mol.
Step-by-step explanation:
To determine the molar mass of a volatile liquid, one must first heat the liquid in a flask with a tiny hole to convert it into a gas. This process is a part of a stoichiometry problem where a student must apply the concept of molar volume at standard temperature and pressure (STP). The molar volume of any gas at STP is 22.4 liters per mole, which is a key piece of information. For the given substance with a vapor density of 1.783 g/L at STP, the formula to calculate the molar mass is:
MM = density of gas × molar volume at STP
Substituting the known values yields:
MM = 1.783 g/L × 22.4 L/mol = 39.9 g/mol
Therefore, the molar mass of the unknown volatile liquid would be approximately 39.9 grams per mole.