# GATE2020: 28

$SO_2$ from air is absorbed by pure water in a counter current packed column operating at constant pressure. The compositions and the flow rates of the streams are shown in the figure.

In addition, use the following data and assumptions

• Column operates under isothermal conditions
• At the operating temperature of the column, $y^*=40x$, where $y^*$ is the mole fraction of $SO_2$ in the gas that is in equilibrium with water containing $SO_2$ at a mole fraction of $x$
• Solution is a dilute and the operating line is linear
• Negligible amount of water evaporates

The number of transfer units (NTU) for this column is

1. $0.5$
2. $1.0$
3. $1.5$
4. $2.0$
in Others
edited