Question

Is \[AlC{{l}_{3}}\] Basic or Acidic?

Answer 1

Hint: We know that the acidic effect of any solution towards litmus then there is release of hydrogen ions in the solution and if any solution shows basic effect towards litmus paper, then there is release of hydroxide ions.

Complete answer: As we know that if the red litmus is changed to blue color, then the solution is basic in nature whereas if the color of blue litmus is changed into red color, then solution is basic. The salt of weak base and strong acid are acidic in nature. The cation of such a salt reacts with water forming a weak base with the release of hydrogen ions ${{H}^{+}}$ in solution. Aluminum chloride is a salt of weak base and strong acid, so it releases hydrogen ions in solutions which impart change in color to litmus paper whereas sodium chloride is a salt of strong acid and strong base. It does not hydrolyze in aqueous solution. Therefore, it does not produce any change in color to litmus paper.
Also, the \[AlC{{l}_{3}}\] is electron deficient. It has three electrons in its valence shell. So, when it forms a covalent compound with chlorine it forms three single bonds with chlorine. Three electrons of aluminium and three electrons of chlorine constitute six electrons in outermost orbit. So, it doesn't form an octet eight electrons in outermost orbit and thus it can take two more electrons by forming a coordinate bond to complete an octet and thus it behaves as Lewis’s acid.
Therefore, the \[AlC{{l}_{3}}\] is acidic in nature.

Note:
Note that the Lewis acid is defined as a compound which can take electrons from a donor compound. These compounds have a tendency to accept lone pairs. This is according to the Lewis concept.