Question

Assertion: Pure water has the maximum water potential.
Reason: Osmotic potential is zero in pure water.
(a)Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
(b)Both Assertion and Reason are incorrect.
(c)Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
(d) Both Assertion and Reason are correct.

Answer 1

The measure of the potential energy in water and the difference between the potential in a given water sample and pure water, is known as water potential.

Complete answer:
Water potential has the tendency of water to flow from one part to the other during various cellular processes and is denoted by the Greek letter Psi. At standard temperature and pressure, the water potential of pure water is considered as zero. This is explained by the kinetic energy possessed by water molecules. The movement of its molecules is rapid and constant when water is in liquid form. Also, pure water has the highest concentration of water molecules. Therefore, it has the highest water potential. The water potential of pure water decreases when some solute is dissolved in water. The osmotic potential of pure water is defined to be zero because there is no solute. But the water potential of pure water in an open container is zero due to the reason that there is no solute and even the pressure in the container is zero. Water potential (Ψ) is given by taking osmotic (or solute) potential (ΨS) and pressure potential (ΨP) and is determined by the formula:
$\Psi \quad ={ \quad \Psi }_{ S }\quad +\quad { \Psi }_{ P }$

So, the correct answer is ‘Both Assertion and Reason are correct and Reason is the correct explanation for Assertion’.

Note: Osmotic potential can be said as the potential of water particles to flow from a hypotonic solution (more water, fewer solutes) to a hypertonic solution (less water, more solutes) across a semipermeable membrane.