Question

Assertion: Anhydrous $MgC{l_2}$ is prepared by heating $MgC{l_2}.6{H_2}O$ in a current of $HCl$ gas
Reason: Presence of $HCl$ gas checks up the hydrolysis of $MgC{l_2}$ by its water of crystallization.
(A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion
(B) Both Assertion and Reason are true and Reason is not the correct explanation of Assertion
(C) Assertion is true but Reason is false
(D) Assertion is false but Reason is true

Answer 1

Hint: $MgC{l_2}$ is a chemical compound, known as Magnesium Chloride. Anhydrous $MgC{l_2}$ contains nearly $25.5\% $ magnesium by mass. It is highly soluble in water. Thus, hydrolysis of $MgC{l_2}$ can prevent the formation of anhydrous $MgC{l_2}$

Complete Step by Step Solution:
Magnesium chloride is a chemical compound with molecular formula, $MgC{l_2}.$ Magnesium chloride has various hydrides with general formula $MgC{l_2}.{({H_2}0)_n}$. These salts are typical ionic halides and are highly soluble in water. When we heat \[MgC{l_2}.6{H_2}O\] directly, we do not get anhydrous $MgC{l_2}$. Because the hydrolysis of anhydrous $MgC{l_2}$ takes place as soon as it breaks down.
So, to get anhydrous $MgC{l_2}$, we need to heat a hydrated $MgC{l_2}$ vacuum, in a current of dry $HCl$ gas. Presence of $HCl$ gas checks up the hydrolysis of $MgC{l_2}$ by its water of crystallization which helps in the formation of anhydrous $MgC{l_2}$ from \[MgC{l_2}.6{H_2}O\].
Thus, we can conclude that the assertion is correct and also we can observe that the reason given for the assertion is also true.

Therefore, from the above explanation the correct option is (A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Note:
\[MgC{l_2}\]is highly soluble in water. In water it dissociates to ions, namely, $M{g^{2 + }}$ and $C{l^ - }$. Therefore, prevention of hydrolysis of \[MgC{l_2}\] is very important to get anhydrous \[MgC{l_2}\]. \[MgC{l_2}\] is the major raw material for the extraction of magnesium. It also has many uses like, dust control and de-icing of highways in low temperature areas. It is also used as a commercial catalyst.