For CH3CH2O- + C6H5OH CH3CH2OH + C6H5O- in water at 298 K (pKa: ethanol 15.9, phenol 10.0), the equilibrium constant is closest to

JEE Advanced levelSingle correct optionDifficulty 3 of 3g2096

For $CH X_{3} CH X_{2} O X^{-} + C X_{6} H X_{5} OH CH X_{3} CH X_{2} OH + C X_{6} H X_{5} O X^{-}$ in water at 298 K (pKa: ethanol 15.9, phenol 10.0), the equilibrium constant is closest to

K = K_{a} (phenol) / K_{a} (ethanol) = 1 0^{- 10.0} /1 0^{- 15.9} = 1 0^{5.9} = 7.9 \times 1 0^{5}

, so ethoxide deprotonates phenol almost completely.