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 0.0093 mole

At standard conditions, 1 liter of air at $21\%$ oxygen possesses 0.21 L of oxygen. Since at STP 1 mole of gas occupies 22.4 L, simply divide $\frac{0.21}{22.4}$, to arrive at 0.0093 moles of oxygen.