a. Assuming the flask has only air in it and that we can treat air as an ideal gas,
pV = nRT gives us, when the stoppered flask is heating up, that
(p/T)_a = (p/T)_b since V and n are constant.
1atm / 296K = p / 373K
p = 1.26 atm ◄ maximum
b. At STP, our flask holds
2.9L * 1mol/22.4L = 0.1295 moles
But we're not at STP. Holding V and p constant,
0.1295mol * 273K = n * 296K
n = 0.1194 mol
When we unstopper, we can hold V and T constant:
1.26atm / 0.1194mol = 1atm / n'
n' = 0.0948 mol
which means that n - n' = 0.0246 mol has escaped
c. When we stopper it up and let it cool, we can hold V and n constant:
1atm / 373 = p / 296
p = 0.79 atm
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