The selectivity of chlorobenzene for pyridine in this system is approximately 1.71.
Extract:
* Pyridine: 19 weight%
* Chlorobenzene: 79.9 weight%
Raffinate:
* Pyridine: 11.1 weight%
* Chlorobenzene: 88.9 weight%
Calculation:
Selectivity = (Pyridine concentration in extract) / (Pyridine concentration in raffinate)
Selectivity = (19 weight%) / (11.1 weight%)
Selectivity ≈ 1.71
Therefore, the selectivity of chlorobenzene for pyridine in this system is approximately 1.71. This means that chlorobenzene preferentially extracts pyridine from the aqueous solution over water, with a ratio of about 1.71 to 1.