Question

What will be the number of moles of oxygen in one litre of air containing 21% Oxygen by volume under standard conditions?

• A. 0.003
• B. 0.006
• C. 0.009
• D. 0.012

Answer 1

The correct option is C

0.009

$100ml$ of air at STP contains $21ml$ of $O_2$

$1000ml$ of air at STP contains = $\frac{21}{100}\times 1000=210ml{O}_2$

$\therefore$ No. of moles = $\frac{Vol.inmlunderSTPconditions}{22400ml}$

= $\frac{210}{22400}=0.009mole.$