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

Answer: (A)

0.0093 mole

Answer 2

(a) Volume of oxygen in 1 L of air
$\frac{21}{100} \times1000$ = 210mL
$\therefore$ 22400 mL volume at STP is occupied by oxygen = 1 mole
Therefore, number of moles occupied by 210 mL
$\frac {210}{22400}$
$\, \, \, = 0.0093 mol$