Question

A gas cylinder contains $12\times {10}^{24}$ molecules of oxygen gas.
If Avogadro's number is $6\times {10}^{23}$; Calculate:
(i) the mass of oxygen present in the cylinder.
(ii) the volume of oxygen at S.T.P. present in the cylinder. $[O=16]$.

Answer 1

(i) $Massofamolecule=\frac{No.ofmolecules}{N_A}$ $\times Molecularmass$

$=\frac{12\times {10}^{24}}{6\times {10}^{23}}\times 2\times 16$

= 640g.

(ii) $Volumeofamolecule=\frac{No.ofmolecules}{N_A}$ $\times Molecularvolume$

$=\frac{12\times {10}^{24}}{6\times {10}^{23}}\times 22.4$

= 448 litres.