Chemical Engineering - Mass Transfer - Discussion

The Correct answer is option c.

When steam distils nitrobenzene at 1 atm pressure, the boiling point of nitrobenzene itself (210. 6°C) is not the relevant temperature for distillation. During steam distillation, the mixture of steam and nitrobenzene will have a boiling point lower than the boiling point of nitrobenzene due to the lowered partial pressure of nitrobenzene over the water.

Since nitrobenzene is steam distilled, it will boil at a temperature significantly lower than its pure boiling point.
In this process, the boiling point is typically between the boiling point of water (100°C) and the boiling point of the substance being distilled (210. 6°C).

We can find the temperature at which this occurs by looking for a temperature where:
Pwater​(T) + Pnitrobenzene​(T) = 101.3kPa.
So, at 99°C, the total vapor pressure equals atmospheric pressure.

Nitrobenzene (C6 H5 NO2) can be distilled with steam under one atmosphere pressure at a temperature of 372.2 K.

How it happened?

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How? Please explain.