Answer
89.46 g/mol
Work Step by Step
We are given that the mass of vapor is 1.012g, the volume of the bulb is 354 $cm^3$, the pressure is 742 torr and the temperature is 99C. To find the molar mass, we can use the formula M = dRT/P, but first we need to find the density. Given that 1.012g takes up a volume of 354$cm^3$ we need to convert the 354 $cm^3$ in to Liters. Given that a cubic centimeter, or cc ($cm^3$) is equivalent to a mL, then we have 354mL, which is 0.354L. Then we have 1.012g/0.354L = 2.859 g/L. We now convert the pressure from torr to atm:
742 torr * (1 atm/ 760torr) = 0.976 atm
and the temperature to Kelvin by adding 273, which is 372K
Last we have M = dRT/P = (2.859 g/L * 0.0821 * 372K) / 0.976 atm = 89.46 g/mol
