Question

The number of mole of oxygen in one litre of air containing 21% oxygen by volume, under standard conditions is:

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

Answer 1

The correct option is A $0.0093mole$

Volume of oxygen = $\frac{21}{100}\times 1=0.21litres=210c{m}^3$

at STP, 1 mole oxygen = 22414 cm${}^3$

Therefore moles of oxygen = $\frac{210}{22414}$ moles =0.0093

Therefore, number of moles of oxygen are 0.0093 moles