JEE Main levelSingle correct optionDifficulty 2 of 3sb186
Washing soda is added to water whose hardness is due to CaSOX4. The calcium-containing solid that separates is
ACa(HCOX3)X2
BCaCOX3
CCa(NaCOX3)X2
DCa(OH)X2
Answer: B
Carbonate ions precipitate calcium: NaX2COX3+CaSOX4CaCOX3+NaX2SOX4. Ca(HCOX3)X2 is soluble, and Ca(OH)X2 is not formed because the solution lacks enough OHX− to precipitate it.