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Question: Answered & Verified by Expert
Aluminium reacts with $\mathrm{NaOH}$ and forms compound ' $X$ '. If the coordination number of aluminium in ' $X$ ' is 6 , the correct formula of $X$ is
Chemistrys Block ElementsVITEEEVITEEE 2009
Options:
  • A $\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}(\mathrm{OH})_{2}\right]^{+}$
  • B $\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{3}(\mathrm{OH})_{3}\right]$
  • C $\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{OH})_{4}\right]^{-}$
  • D $\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right](\mathrm{OH})_{3}$
Solution:
2948 Upvotes Verified Answer
The correct answer is: $\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{OH})_{4}\right]^{-}$
$2 \mathrm{Al}+2 \mathrm{NaOH}+2 \mathrm{H}_{2} \mathrm{O} \longrightarrow \underset{\begin{array}{c}\text { sodum meta } \\ \text { aluminata }\end{array}}{\mathrm{NaAlO}_{2}}+3 \mathrm{H}_{2}$ Sodiummetaaluminate, thus formed, is soluble in water and changes into the complex $\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{OH})_{4}\right]^{-}$, in which coordination number of $\mathrm{Al}$ is 6 .

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