In a solvent \( S \), a compound \( B \) is partially dissociated into \( C \) and \( D \) as given below:
\( B \rightleftharpoons 2C + 2D \)
\( B, C \) and \( D \) are non-volatile in nature. The molar mass of \( B \) is \( 10 \) times the molar mass of \( S \). The standard boiling point and the standard enthalpy of vaporization of \( S \) are \( 400 \, \text{K} \) and \( 10R \, \text{J mol}^{-1} \), respectively \( (R \) is the gas constant in \( \text{J K}^{-1} \text{ mol}^{-1}) \). A solution of \( B \) in \( S \) with an initial concentration of \( B \) as \( 0.25\% \) (mass/mass) has a boiling point of \( 408 \, \text{K} \) at \( 1 \) bar pressure. In this solution, the mole percent of \( B \) that has been dissociated is ________.
