Saturday, July 20, 2013

A 0.230 L sample of helium gas at 25.0°C is held in a container with a movable piston which maintains a constant pressure of 1.00 atm. If the gas...

This problem can be solved using Charles's Law, which states that the Kelvin temperature and the volume of a gas are directly related when the pressure is held constant. Mathematically, it's written as follows:


`V_1/T_1 = V_2/T_2`


Rearranging to isolate V2 gives us


`V_2 = (V_1T_2)/T_1 `


V1 = 0.230 Liters


V2 = unknown


T1 = (25.0ºC + 273) = 298 K


T2 = (73ºC + 273) = 346 K


V2 = (0.230 L)(346 K)/(298 K)


V2 = 0.267 Liters


The pressure is given but isn't part of  the calculation because it remains constant. The moveable piston allows the pressure inside the cylinder to equalize with the pressure outside as the volume changes.


Celsius temperatures have to be converted to Kelvins for gas law calculations becasue the Celsius scale isn't proportioanal. 

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