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Question: The ideal gas law , PV= nRT can be used to predict the changes in Pressure, Temperature, and Volu...
The ideal gas law , PV= nRT can be used to predict the changes in Pressure, Temperature, and Volume. R = 82.06 cc-atm/deg-mol.
a. If you have a sealed core tube containing 21% O2, how many millimoles of O2 would that be if there was 500cm^3 of head space at 25 degrees celcius and 1 atm?
b. How would that change if the temperature of the tube was 85 degrees celcius?
Explanation / Answer
a) Use the equation PV = nRT to first calculate the total moles
Pressure P = 1 atm
Temperature = 25 C = 298 k
Volume = 500 cm3.
(1 atm)x(500 cm3) = n x (82.06 cm3-atm/deg K-mol)x(298 K)
n = 0.02045 moles = 20.45 mmoles
Now O2 is 21 % therefore millimoles of O2 = (21/100) x 20.45
= 4.2945 millimoles
b) Since the core tube is sealed the volume and the total moles will remain unchanged on increasing the temperature.
Increasing temperature to 85 C will increase the presssure in the sealed core tube.
The pressure when the temperature becomes 85 C or 358 K will be
Px(500 cm3) = (0.02045) x (82.06 cm3-atm/deg K-mol)x(358 K)
P = 1.20 atm
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