Question

Why is the nacl extracted with water three times as opposed to only once?

Answer 1

The NaCl is extracted three times to get maximum amount of it. Each extraction only yeilds about 50% of the NaCl from the water. So, after the tird extraction, you would have recieved around 87.5% of the total amount of NaCl from the water(50%+25%+12.5%). After the third extraction, the amount of salt in the water will only be a small amount.