Reverse Osmosis and desalinating water
Question:

Desalination technology has been around for the better part of the last century, this technology has brought fresh water and hence industrial and commercial development to areas of the world that otherwise might have remained unproductive. Not only has development been enhanced by this technology but, more importantly, the health and welfare of many people have been improved by the supply of sanitary fresh water supplies.


In the late 1960s, reverse osmosis (RO) was developed for desalting saline water supplies. This process is based on the principal of osmosis and requires a membrane barrier to separate salts from water. Because RO technology required considerably less energy to operate than distillation, it was considered to be the technology that would make desalination much more attainable to the world’s water scarce areas.

  • This photo shows the difference between osmosis and the reverse osmosis.

  • Watch the video below and answer the question.

Water desalination uses the reverse osmosis principle  that requires external pressure by pumps.

What is the explanation for that?


  

2 People tried to answer this question

Pressure is important to speed up the process and save time. 

The pressure must be applied to allow the salt particles pass through the membrane, so we get pure water. 

The pressure must be higher than the osmotic pressure in order to allow water  flow from the pure water to the concentrated solution (seawater) 

The pressure must be higher than the osmotic pressure in order  to allow the water flow from the concentrated solution (seawater) to the pure water. 

Excellent :)

 

try again.

 

This is the osmosis principle not the revers osmosis. 

 

Thr salt particles cant pass through membrane.

 



Comments:
1.  Hashoul Majdi (27.06.2017 am 01.11.15)
Peer Assessment

Peer Assessment:
The question relates to the issue of "Reverse Osmosis and desalinating water"

The introduction of the question give certain background especially in historic dimension, and the explanation mentioned at the beginning of the video (based on presentation) enable the watcher to understand more about osmosis and reverse osmosis (RO). The pictures and the designed slides helps to understand more this process, and the cursers helps to know the direction of the flow. 

This multi-choice question, included background, video, ends with a question mark, contain feedbacks for the three disturbances but missed a relevant one especially for the following disturbance: "Pressure is important to speed up the process and save time." And the following feedback "wrong answer". I think that the responses for the other disturbances too should be more detailed to help the student not only to understand his mistake but to direct him to the right answer. for example, in the case of the answer "The pressure must be applied to allow the salt particles pass through the membrane, so we get pure water. " and the feedback "The salt particles can’t pass through membrane.", the feedback doesn’t give any indication to the right answer.

It was not easy for me to understand the subject from the introduction, I suggest improving it by replacing the historical details with a simple knowledge that explain the meaning of the basic terms of osmosis, reverse osmosis and desalinating water and the process, especially for students that don't have a relevant background.

The video is beautifully designed, however the first pictures passed very fast, and appeared late in the fourthfifth second. some other slides passed very fast and was better to slow them down. 

Best wishes,

Majdi Hashoul.



History of edits
Edited BY: hafeeza dahley Edit Date: 2017-05-26 15:27:37
Edited BY: hafeeza dahley Edit Date: 2017-05-25 18:09:14
Edited BY: hafeeza dahley Edit Date: 2017-05-24 21:32:27
Edited BY: hafeeza dahley Edit Date: 2017-05-24 19:28:53
Edited BY: hafeeza dahley Edit Date: 2017-05-24 19:27:16
Edited BY: hafeeza dahley Edit Date: 2017-05-24 16:33:17
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