#25
A 10.86 mol sample of krypton
gas is maintained in a 0.7529 L container at
296.3 K. What is the pressure in atm calculated
using the van der Waals' equation for Kr gas under
these conditions? For Kr, a =
2.318L2atm/mol2 and b =
3.978×10-2 L/mol.
____atm
According to the ideal gas law, a 1.077 mol
sample of methane gas in a 1.670
L container at 265.4 K should exert a pressure of
14.05 atm. By what percent does the pressure
calculated using the van der Waals' equation differ from the ideal
pressure? For CH4 gas, a =
2.253 L2atm/mol2 and b =
4.278×10-2 L/mol.
______%
Hint: % difference = 100×(P ideal - Pvan
der Waals) / P ideal
According to the ideal gas law, a 9.308 mol
sample of nitrogen gas in a
0.8235 L container at 502.7 K
should exert a pressure of 466.3 atm. By what
percent does the pressure calculated using the van der Waals'
equation differ from the ideal pressure? For
N2 gas, a = 1.390
L2atm/mol2 and b =
3.910×10-2 L/mol.
%
Hint: % difference = 100 × (P ideal - Pvan
der Waals) / P ideal
.26
A 9.65×10-2 mol sample of an unknown gas contained in a 5.00 L flask is found to have a density of 0.720 g/L. The molecular weight of the unknown gas is _____g/mol.
A 7.01×10-2 mol sample of
Ne gas is contained in a 2.00 L
flask at room temperature and pressure. What is the density of the
gas, in grams/liter, under these conditions?
_______g/L
What is the molar volume of Xe gas under the
conditions of temperature and pressure where its density is
2.84 g/L?
_____ L/mol
25:
krypton gas :
We know the van der Waals' gas equation = [P + a(n/V)^2] [V/n-b] = RT
From the given data a = 2.318 L2atm/mol2 and b = 3.978×10-2 L/mol
Volume V= 0.7529 L, T = 296.3 K, n = 10.86 moles
if plugin all the above values in the equation
[P+ 2.318 L2atm/mol2 (10.86 moles/0.7529 L)^2] [0.7529 L/10.86 moles - 3.978×10-2 L/mol] = 0.0821 L.atm /mole.K x 296.3 K
[P + 482.2791 atm] [2.9547 x 10-2 L/mol] = 24.32623 L.atm/mole
[P + 482.2791 atm] = 8.23306 x 102 atm
P = 341.0269 atm
Methane gas :
Similarly if we calculated for CH4 the pressure calculated using the van der Waals' equation
[P+ 2.253 L2atm/mol2 (1.077 moles/1.670 L)^2] [1.670 L/1.077 moles - 4.278×10-2 L/mol] = 0.0821 L.atm /mole.K x 265.4 K
P = 13.514 atm
Ideal pressure Pi = 14.05 atm
% difference = 100×(P ideal - Pvan der Waals) / P ideal = 100 (14.05-13.514)/14.05 = 3.815 %
Nitrogen gas :
[P+ 1.390 L2atm/mol2 (9.308 moles/0.8235 L)^2] [0.8235 L/9.308 moles - 3.910×10-2 L/mol] = 0.0821 L.atm /mole.K x 502.7 K
177.5825 x 0.04937 =
P = 658.3840 atm
Ideal pressure Pi = 466.3 atm
% difference = 100×(P ideal - Pvan der Waals) / P ideal = 100 (14.05-13.514)/14.05 = - 41.19 %
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