By product in the formation of Na2CO3 by solvay process is :
NaCl
NH3
NH4OH
CaCl2
As we learnt ,
Manufacture of Na2CO3 by solvay process -
Brine (NaCl), ammonia and carbon dioxide are used as raw materials and calcium chloride is formed as a by-product
The reactions are given below:
Therefore, option(4) is correct.