Question

The number of moles of oxygen in 1 L of air containing 21% oxygen by volume, under standard conditions, is

• A. 0.0093 mole
• B. 2.10 moles
• C. 0.186 mole
• D. 0.21 mole

Answer 1

The Correct Option is A

To determine the number of moles of oxygen in 1 liter of air under standard conditions, we can follow these steps:

1. We know that air contains 21% oxygen by volume. This means in 1 liter of air, 21% of that volume is oxygen.

2. Calculate the volume of oxygen in 1 liter of air:

   = 1 \text{ L} \times 0.21 = 0.21 \text{ L of oxygen}

3. Under standard conditions (STP: standard temperature and pressure), 1 mole of any ideal gas occupies 22.4 liters. We can use this to convert volume to moles.

4. Calculate the number of moles of oxygen using the formula:

   \text{Moles of Oxygen} = \frac{\text{Volume of Oxygen at STP}}{22.4 \text{ L/mol}}

5. Substitute the known values:

   \text{Moles of Oxygen} = \frac{0.21 \text{ L}}{22.4 \text{ L/mol}} \approx 0.00938 \text{ mol}

6. Round the value to match the options provided:

   The number of moles of oxygen is approximately 0.0093 mol.

The correct answer is 0.0093 mole.