Question

During the evaporation of cleaned sugarcane juice, pressure surrounding it is reduced to:

• A. increase the boiling point
• B. maintain the boiling point at $373K$
• C. decrease the boiling point
• D. increase the size of the sugar crystals

Answer 1

Answer: (C)

decrease the boiling point

From Clausius-Clapeyron equation,

$ln\left(\frac{P_1}{P_2}\right)=\frac{△H_{vap}}{R}[\frac{1}{T_2}-\frac{1}{T_1}]$

where $P_1$ is the pressure at $T_1$ and $P_2$ is the pressure at $T_2$.

[$T_1$ and $T_2$ are boiling point. Since, at vapor pressure, the temperature is called boiling temperature or boiling point.]

So, if we decrease pressure $P_2$ or surrounding pressure, the $T_2$ boiling temperature at that pressure must decrease.