Question

What is the formula for the basic anhydride of $Ba{{(OH)}_{2}}$?
(a) $B{{a}_{2}}O$
(b) $BaO$
(c) $Ba{{O}_{2}}$
(d) $Ba$

Answer 1

Hint: Usually by losing a water molecule from certain molecules, anhydride is formed. For a hydrated form, we need to add water molecules to anhydride.

Complete step-by-step answer:
Basic anhydride is basically an oxide of a chemical element from group 1 or group 2. These are prepared by removing water molecules from their corresponding hydroxide base and if water is added to the basic anhydride we obtain its hydroxide salt. These basic anhydrides are not Bronsted-Lowry bases as they are not proton acceptors.
So, by removing a water molecule from the hydroxide $Ba{{(OH)}_{2}}$, we get Barium oxide $BaO$.
$Ba{{(OH)}_{2}}\xrightarrow{-{{H}_{2}}O}BaO$
Hence, the formula for the basic anhydride of $Ba{{(OH)}_{2}}$ is $BaO$ .
The correct answer to the question is option (b).

Additional Information:
-Basic anhydrides are not Bronsted-Lowry bases, but they are Lewis bases. They can share an electron pair with some of the other Lewis acids, mostly acidic oxides. They are good alkalis and have the ability to cause alkali burns on skin because of its strong affinity, which react with body water. An example for such an anhydride is quicklime or calcium oxide, which can react with body skin to give hydrated lime or calcium hydroxide causing alkali burn.
-Another examples for basic anhydrides are LiO (which in reaction with water gives lithium hydroxide), sodium oxide(which in reaction with water gives strong base sodium hydroxide) and etc.

Note: From the hydroxide, when a water molecule is removed, two hydrogen and oxygen is removed. So, what is left are one Barium atom and one oxygen atom, that is barium oxide.