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This mixture contains 1.96 g He and 60.8 g O2 confided in a 5.00 L tank at 25.0 degrees celsius. What are:

A) the mole fractions of two gases?
B) their partial pressures?
C) total pressure?

find moles, using molar masses:
1.96 g He @ 4.00 g/mole = 0.49 moles Helium

60.8 g O2 @ 32.0 g/mol = 1.90 moles oxygen

total moles = 2.39 moles
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A) the mole fractions of two gases?

Helium:
0.49 moles Helium / 2.39 total moles = 0.205 helium’s mole fraction

1.90 mole O2 / 2.39 total moles = 0.795 oxygen’s mole fraction

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B) their partial pressures?

first find total pressure:
PV=nRT
P(5.00L) = 2.39 moles (0.08206 Litre-atm / mol-K)(298K)
total pressure = 11.69 atm

B) their partial pressures?
Helium:
11.69 (0.205 helium’s mole fraction) = 2.396 atm Helium
your answer(3sigfigs): 2.40 atm Helium partial pressure

Oxygen:
11.69 – 2.40 = 9.29 atm oxygen
your answer is: 9.29 atm Oxygen partial pressure
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C) total pressure?

your answer(3sigfigs): 11.7 atm

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