Conversion reaction (Chemical reaction) of Calcium carbonate to 1,2- dichloromethane????
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Answer:
Upon a lengthy storage under aerobic conditions chloroform is converted slowly to phosgene (COCl2), releasing HCl in the process.
2 CHCl3 + O2 → 2 COCl2 + 2 HCl
To prevent such reaction, commercial chloroform is stabilized with ethanol or amylene. Phosgene and HCl can be removed from chloroform by washing with saturated aqueous carbonate solutions, such as sodium bicarbonate. This procedure is simple and results in harmless products. Phosgene reacts with water to form carbon dioxide and HCl, and the carbonate salt neutralizes the resulting acid.
Suspected samples can be tested for phosgene using filter paper (treated with 5% diphenylamine, 5% dimethylaminobenzaldehyde in ethanol, and then dried), which turns yellow in phosgene vapor. There are several colorimetric and fluorometric reagents for phosgene, and it can also be quantified with mass spectrometry.
Further, if traces amounts of HCl are present the latter may react with Ca(CO3)2 to furnish CaCl2, CO2 and water.
Please note that it might be difficult to observe changes upon titration of (tiny amounts) traces of HCl with silver nitrate.