To answer this item, it is assumed that O2 is an ideal gas such that it follows the ideal gas law.
PV = nRT
Solving for n,
n = PV / RT
where n is number of moles, P is pressure, V is volume, R is the universal gas constant, T is the temperature.
Substituting the known values,
n = (724 mmHg/760 mmHg/1 atm)(1 L) / (0.0821 L. atm/mol.K)(298 K)
Simplifying,
n = 0.0389
Hence, the value of n is 0.0389.
