JEE Main levelSingle correct optionDifficulty 2 of 3sb143
In the Solvay process NaHCOX3 crystallises from the cold ammoniacal brine, rather than NHX4HCOX3, NaCl or NHX4Cl, because:
Ait is the only salt formed in the reaction
Bit has the highest lattice enthalpy of all four salts
Cit is the only one that is not hydrated
Dit has the lowest solubility of the four possible salts under these conditions
Answer: D
The solution contains NaX+, NHX4X+, ClX− and HCOX3X−, so four salts are possible in principle. Of these, NaHCOX3 is the least soluble in the cold, and so it precipitates first and is filtered off.