Question

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

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

Answer 1

The correct option is D $0.0093$ mol

$1L$ of gas containing $21\%$ of oxygen.

Hence, volume of oxygen in $1000mL$ of air $=\frac{21}{100}\times 1000=210mL$

Since $22400ml$ volume at $STP$ is occupied by $1mole$ of oxygen.

Number of moles occupied by $210ml$ $=\frac{210}{22400}=0.0093moles$

Hence, option $D$ is correct.