When the reaction mixture is worked-up, it is first washed three times with 5% sodium bicarbonate, and then with a saturated nacl solution. explain why?

Solution:

After the reaction of mixture is worked-up Washing three times the organic  with sodium carbonate helps to decrease the solubility of the organic layer into the aqueous layer. This allows the organic layer to be separated more easily.

And then the reaction washed by saturated NACL we have The bulk of the water can often be removed by shaking or "washing" the organic layer with saturated aqueous sodium chloride (otherwise known as brine). The salt water works to pull the water from the organic layer to the water layer.

level 4 to level 2 : ))

nuclear fission produces elements that are heavier than helium.

the elements that are used in nuclear fission and their products are much heavier than helium.