Give reasons for the following:

Options

A. Why is calcium preferred over sodium to remove last traces of moisture from alcohol?
B. A piece of burning magnesium ribbon continues to burn in `SO_(2)`.
C. Halides of `Be` are soluble in organic solvents, while those of `Ba` are insoluble
D. `BeCl_(2)` fumes in moist air, but other alkline earth metal chloride do not.

Explanation

(a). Both calcium and sodium react with water to form their respective hydroxides.
`Ca+2H_(2)OrarrCa(OH)_(2)+H_(2)`
`2Na+2H_(2)Orarr2NaOH+H_(2)`
Sodium reacts vigorously with alcohol to form sodium ethoxide, but calcium reacts very slowly.
`2Na+2ROHrarrunderset("Sodium ethoxide")(2RONa+H_(2))`
`2Ca+2ROHrarr2ROCa+H_(2)`
Thus, when calcium is used, it reacts more readily with water rather tahn sodium.
(b). A piece of burning `Mg` continues to burn in `SO_(2)`, since it produces `MgO` and `S`.
`Mg+SO_(2)overset(Delta)(rarr)MgO+S`
The reaction is highly exothermic and the heat produced keeps the magnesium ribbon burning.
(c ). Halides of `Be` are covalent due to high polarising ability of `Be^(2+)` ion, hence they are soluble in orginic solvents. whereas halides of `Ba` are ionic and thus are insoluble in organic solvents.
(d). `BeCl_(2)` being a salt of weak base `Be(OH)_(2)` and strong acid `(HCl)` gets hydrolysed to from `HCl`, which fumes in air.
`BeCl_(2)+2H_(2)OrarrBe(OH)_(2)+2HCl`
But other alkaline earth metal chloride `MCl_(2)` being salt of strong base `[M(OH)_(2)]` and strong acid `(HCl)` do not undergo hydrolysis and hence no fames of `HCl` are produced.