Question

For a solution at atmospheric pressure :

• A. ${\psi }_w={\psi }_s$
• B. ${\psi }_w=0$
• C. ${\psi }_s=0$
• D. None of above

Answer 1

The correct option is A ${\psi }_w={\psi }_s$

Free energy is the potential to do work and the free energy of water is 'water potential', given by
${\psi }_w={\psi }_s+{\psi }_p$, where
${\psi }_s=$ solute potential
${\psi }_p=$ pressure potential
At atmospheric pressure, there is no net hydrostatic pressure of the solution.
$\therefore$ The pressure potential at atmospheric pressure is zero.
$\therefore {\psi }_w={\psi }_s$