The volume occupied by 3.2 g of oxygen at STP is:
Correct answer: B. 2.24 dm3
- A. 22.4 dm3
- B. 2.24 dm3
- C. 11.2 dm3
- D. 16.0 dm3
Explanation
At STP, one mole of any ideal gas occupies 22.4 dm3. The molar mass of oxygen (O2) is 32 g/mol. Therefore, the number of moles in 3.2 g of oxygen is 3.2 g / 32 g/mol = 0.1 moles. The volume occupied by 0.1 moles of oxygen is 0.1 × 22.4 dm3 = 2.24 dm3.Option A represents the full molar volume at STP, not applicable to 3.2 g. Option C is half the molar volume, applicable to 16 g of oxygen, not 3.2 g. Option D does not correlate with any significant fraction of molar volume in this context.
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About Standard Temperature and Pressure
Standard temperature and pressure provide reference conditions for gas calculations: 0°C or 273 K and, in the usual school convention, 1 atm pressure. Questions use these conditions to relate pressure, volume, temperature and amount of gas, including the molar volume of an ideal gas, about 22.4 dm³.
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