# Problem: The mass of an evacuated 255-mL flask is 143.187 g. The mass of the flask filled with 268 torr of an unknown gas at 25 oC is 143.290 g .Calculate the molar mass of the unknown gas.

###### FREE Expert Solution

Using the ideal gas equation.

$\overline{){\mathbf{P}}{\mathbf{V}}{\mathbf{=}}{\mathbf{n}}{\mathbf{R}}{\mathbf{T}}}$

Isolate n (number of moles of gas):

###### Problem Details

The mass of an evacuated 255-mL flask is 143.187 g. The mass of the flask filled with 268 torr of an unknown gas at 25 oC is 143.290 g .

Calculate the molar mass of the unknown gas.