The volume of nitrogen gas `Vm` (at STP) required to cover a sample of silica gel with a monomolecular layer is `129cm^(3)g^(-1)` of gel. Calculate the surface area per gram of the gel if each nitrogen molecule occupies `16.23xx10^(-20)m^(2)` .

Explanation

`22400cm^(3)` of `N_(2)` at STP contain `=6.023xx10^(23)` molecules
`:.129cm^(3)` of `N_(2)` at STP will contain
`=(6.023xx10^(23)xx129)/(22400)=3.468xx10^(21)` molecules
Area occupied by a single molecule `=16.2xx10^(-20)m^(2)`
Therefore, area occupied by `3.468xx10^(21)` molecules of `N_(2)=(162.2xx10^(-20))xx(3.468xx10^(21))m^(2)=561.8m^(2)`
Therefore, surface area per gram of gel `=561.8m^(2)`