Question

Describe the method of obtaining salt from sea water.

Answer 1

Hint: There are various methods used for getting salt from sea water. One can be by heating the solution resulting in evaporation of water. Another could be by forcefully removing water through a filter. As a result, salt is left behind.

Complete step by step answer:
We all know that the sea contains a large number of ions dissolved in its water. The common rock salt NaCl is also obtained from sea. There are various methods by which we can obtain salt from the sea water.
The one of the simplest methods is that the sea water is allowed to stand in small shallow pits. When the sunlight fall on this water, the water evaporates in a few days. The solid salt is left behind which then undergoes some purification processes to give pure NaCl that is fit for consumption. This process can be done at home by putting sea water in a shallow container and then allowed to heat it. Such a method is called the Evaporation method and widely used near sea areas.
Another method used can be reverse osmosis. In reverse osmosis method, the water is forcefully passed through a permeable filter. As a result, the concentration of salt increases when the water is pushed out. This method can be used only for a few Litres of separation because it is very expensive.
There is one more method called Electrodialysis. In this process, The water is put in a large container and then a negatively charged anode and a positively charged cathode are placed in this water which are separated by a porous membrane. After this, the electric current is passed, the anode attracts the positive sodium ions while the cathode attracts the negative chloride ions. As a result, the water is left behind. Thus, salt gets separated from the water.
One more method is involving use of chemicals. The decanoic acid is added to the sea water in a container and then the solution is heated. After some time, the solution is cooled. On cooling, the salt is produced in the form of precipitates at the bottom of the container. The water and decanoic acid forms two layers which can be separately removed.

Note: During evaporation, the surface area of the container or pit has to be large. Because the rate of evaporation is directly proportional to area.
In electrodialysis, the water left is not fit for consumption because the anode and cathode attract the charged particles only. The uncharged particles remain as such in the water only.