Question

$0.1M$solution of solute (non-electrolyte) will have a water potential of
A. $ - 2.3$bars
B. Zero
C. $2.3$ bars
D. $22.4$ bars

Answer 1

Hint: All living organisms, including plants, require free energy to grow and reproduce. In thermodynamics, free energy tells us the potential to do work. The free energy of water is usually considered to have water potential. It is represented by symbol $ \varphi _P $

Complete answer:
By standard conditions the water potential of pure water at standard temperatures, which is not under any pressure, is taken to be zero.
When some amount of solute is dissolved in pure water, the solution now becomes deficient in free water and the concentration of water decreases, reducing its water potential.
All living organisms, including plants, require free energy to grow and reproduce. In thermodynamics, free energy represents the potential to do work.

The free energy of water is referred to as water potential. It is represented by symbol $ \varphi _S $
For a solution at atmospheric pressure (water potential) $ \varphi _W $ = (solute potential) $ \varphi _S $, If the pressure greater than atmospheric pressure is applied to pure water or a solution, its water potential increases. Now let us calculate the water potential:

Water potential\[ = - iCRT\], where, $i = $ ionization constant
$C = $ Molar concentration
$R = $ Pressure constant, that is \[0.0831{\text{litre bar}} \; mol^{ - 1}K^{ - 1}\]
$T = $ Temperature in $K$, that is \[273{\text{ }}K\].
In the given problem, \[C = 0.1{\text{ }}M\]
$\therefore$, water potential \[ = - 1 \times 0.1 \times 0.0831 \times 273 = - 2.3{\text{ }}bars\].

Hence, the correct answer is option (A).

Note: Water potential is also defined as potential of water that is chemical in nature means chemical potential. The higher the concentrations of water in a system, the more will be its kinetic energy or water potential'. Water moves from the point where water potential is highest and it goes, to the other point where water potential is less. It can also be said that the difference in water potential between two points is a measure of the amount of work (energy) needed to move water from one point to another.