Explain the phenomenon of reverse osmosis.
OR
How can pure water be obtained from sea water or from ocean ?

Explanation

The phenomenon of the passage of solvent like water under
high pressure from the concentrated aqueous solution like sea water
into pure water through a semipermeable membrane is called reverse
osmosis.
The osmotic pressure of sea water is about 30 atmospheres. Hence
when pressure more than 30 atmospheres is applied on the solution
side, regular osmosis stops
and reverse osmosis starts.
Hence pure water from sea
water enters the other side of
pure water.

For this purpose of suitable semipermeable mem-
brane is required which can
withstand high pressure
conditions over a long period.
This method is used successfully in Florida since 1981 producing
more than 10 million litres of pure water per day.