• question_answer Why is calcium preferred over sodium to remove last traces of moisture from alcohol?

Both Na and Ca react with water to form their respective hydroxides. On the other hand, Na readily reacts with alcohol to form sodium ethoxide but Ca reacts only very slowly. Thus, when Ca is used, it will react more readily with water than with alcohol. $2{{C}_{2}}{{H}_{5}}OH+2\,Na\xrightarrow{\,}\,2\,{{C}_{2}}{{H}_{5}}ONa+{{H}_{2}}$ Therefore, Ca is preferred over Na to remove the last traces of moisture from alcohol.