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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Fury

Chemistry

27 September, 02:48

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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Roy Key · 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