Phenol reacts with dilute \(\mathrm{HNO}_{3}\) at \(40^{\circ} \mathrm{C}\) to give a mixture of ortho and para nitro phenols. They are readily separated by (a) filtration (b) solvent extraction (c) steam distillation (d) fractional crystallization

Filtration is a separation technique used when there is a solid-liquid or solid-gas mixture. It involves the use of a porous membrane or filter paper to retain the solid particles and allow the liquid or gas to pass through. In our case, both ortho and para nitro phenols are in the liquid state in the reaction mixture, so filtration would not be able to separate them.

Solvent extraction involves the use of a solvent that selectively dissolves one or more components in a mixture, leaving the other components behind. The dissolved components are then separated from the solvent by methods like evaporation, distillation, or precipitation. While this method could potentially separate ortho and para nitro phenols if a suitable solvent is found, it might not be the most efficient option available.

Steam distillation is a technique used to separate volatile organic compounds from non-volatile or high boiling-point compounds by using water vapor. The volatile components in the mixture are carried away by steam and can be separated and collected through condensation. However, this method is not suitable for our case since both ortho and para nitro phenols have relatively high boiling points and are not readily carried away by steam.

Fractional crystallization is a separation technique that takes advantage of the different solubilities of compounds in a solvent. When the mixture is cooled or the solvent is allowed to evaporate, crystals of the less soluble compound will form first, while the more soluble compound remains in the solution. The crystals can then be separated by filtration or another appropriate method. This technique is suitable for separating ortho and para nitro phenols since they have different solubilities and can be selectively crystallized at different temperatures or concentrations. Based on our analysis of the four separation methods, we can conclude that: Phenol reacts with dilute \(\mathrm{HNO}_{3}\) at \(40^{\circ} \mathrm{C}\) to give a mixture of ortho and para nitro phenols. They are readily separated by: (a) filtration - Incorrect (b) solvent extraction - Possibly, not the most efficient (c) steam distillation - Incorrect (d) fractional crystallization - Correct