Question

A 12-L oxygen tank is maintained at room temperature and is filled (with O2) to an absolute pressure of 7.2 MPa. If a person can survive on 32 g hr-1 of O2, how long could a person survive on the oxygen in the tank? (show your steps of calculation)

Answer 1

Using the ideal gas equation,
P * V = n * R * T,
Where P, V, n are the pressure, volume and number of moles of the gas, R is the universal gas constant and T is the temperature.
P = 7.2 MPa = 7.2 * 10⁶ Pa
V = 12 L = 12 * 10^-3 m³
T = 300 K
n = (P * V) / (R * T)
= (7.2 * 10⁶ * 12 * 10^-3) / (8.314 * 300)
= 34.64 mol
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1 mol contains 32 g of oxygen.
34.62 mol contains 34.64 * 32 g of oxygen.
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Oxygen consumption in 1 hour = 32 g.
Number of hours the oxygen will last = (34.64 * 32) / 32
= 34.64 hours