The by-product of Solvay-ammonia process is: CO2, NH3, CaCl2, CaCO3

CaCl2 is produced as a by-product in Solvay ammonia process:
NaCl + CO2 + NH3 + H2O → NaHCO3 + NH4Cl
CaCO3 → CO2 + CaO
2NH4Cl + CaO → 2NH3 + CaCl2 (by-product) + H2O
Sodium carbonate is manufactured by Solvay ammonia process. The raw materials are brine (NaCl), ammonia and carbon dioxide. Hence, option C is correct.