At `727^(@)C` and `1.2 atm` of total equilibrium pressure, `SO_(3)` is partially dissociated into `SO_(2)` and `O_(2)` as:
`SO_(3)(g)hArrSO_(2)(g)+(1)/(2)O_(2)(g)`
The density of equilibrium mixture is `0.9 g//L`. The degree of dissociation is:, `[Use R=0.08 atm L mol^(-1) K^(-1)]`
A. `1//3`
B. `2//3`
C. `1//4`
D. `1//5`