If the volume occupied by oxygen gas (O₂) at STP is 44.8 dm³, the number of molecules of O₂ in the vessels are:

Here are the solutions to the multiple-choice questions:

• i) If the volume occupied by oxygen gas (O₂) at STP is $44.8 \text{ dm}^3$, the number of molecules of O₂ in the vessels are:

  Step 1: Determine the number of moles of O₂.
  At STP, 1 mole of any gas occupies $22.4 \text{ dm}^3$.

  $$\text{Moles of O}_2 = \frac{\text{Given volume}}{\text{Molar volume at STP}} = \frac{44.8 \text{ dm}^3}{22.4 \text{ dm}^3/\text{mol}} = 2 \text{ mol}$$

  Step