A 0.642g sample of an unknown gas was collected over water at 25.0°C and 1.04 atm. The collection cylinder contained 151.3 mL of gas after the sample was released. Find the molar mass of the unknown gas.

Question

Chemistry

Tristin Cantu

28 July, 02:56

A 0.642g sample of an unknown gas was collected over water at 25.0°C and 1.04 atm. The collection cylinder contained 151.3 mL of gas after the sample was released. Find the molar mass of the unknown gas.

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Julissa Best · Answer 1

Molar Mass = 99.7669.

To solve, first use the equation PV=nRT and solve for n, the number of moles. You do this by finding that n=PV/RT. Then plug in your values above, make sure your temperature is in kelvins by adding 273 and your volume is in liters (151.3 mL = 0.1513 L). You get that n=.006435. You can then solve for the molar mass by dividing your given mass, 0.642g, by the number of moles you solved for,.006435, and get 99.7669 g/mol