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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3qc201

Which statements about the hydroxides of group III cations are correct?

A $Fe (OH) X_{3}$ does not dissolve in excess NaOH
B $Cr (OH) X_{3}$ dissolves in excess NaOH to give green $[Cr (OH) X_{4}] X^{-}$
C $Al (OH) X_{3}$ dissolves in excess aqueous $NH X_{3}$
D $Fe X^{3 +} (aq)$ solutions are acidic due to hydrolysis

Answer: A, B, D

Fe(OH)3 is basic, Cr(OH)3 and Al(OH)3 are amphoteric and dissolve in excess strong base. Aluminium hydroxide does not dissolve in excess aqueous ammonia (weak base, low

[OH X^{-}]

). Hydrolysis

[Fe (H X_{2} O) X_{6}] X^{3 +} [Fe (OH) (H X_{2} O) X_{5}] X^{2 +} + H X^{+}

makes the solution acidic. Options 1, 2 and 4.

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