How many moles of oxygen (O2) are present in 33.6 L of the gas at 1 atm and 0°C?

At 1 atm and 0°C, 1 mole of an ideal gas occupies 22.4 L. Divide the given volume by the molar volume: 33.6 L ÷ 22.4 L/mol = 1.5 mol. Therefore, the correct choice is 1.5.

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