Question

Given below are two statements :
Statement I : Aluminium upon reaction with NaOH forms $[Al(OH)_6]^{3-}$ ion.
Statement II : The geometry of $ICl_4^-$, $ClO_3^-$ and $IBr_2^-$ is square planar, pyramidal and linear respectively.
In the light of the above statements, choose the correct answer from the options given below :

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Statement I involves the reaction of amphoteric metals with strong bases. Statement II involves VSEPR theory and the prediction of molecular geometry.
Step 2: Detailed Explanation:
Analysis of Statement I:
Aluminium reacts with NaOH to form sodium tetrahydroxoaluminate(III) and hydrogen gas:
\[ 2\text{Al} + 2\text{NaOH} + 6\text{H}_2\text{O} \to 2\text{Na}[Al(OH)_4] + 3\text{H}_2 \uparrow \]
The predominant ion formed is the tetrahedral $[Al(OH)_4]^-$ ion, not the octahedral $[Al(OH)_6]^{3-}$. Thus, Statement I is False.

Analysis of Statement II:
1. $ICl_4^-$: $I$ has 7 valence electrons + 1 (charge) $= 8$. 4 Bond pairs, 2 Lone pairs. Steric number $= 6$ ($sp^3d^2$). Geometry: Square Planar.
2. $ClO_3^-$: $Cl$ has 7 valence electrons + 1 (charge) $= 8$. 3 oxygen atoms use 6 electrons for bonds (assuming 1 double bond each). 1 Lone pair remains. Steric number $= 4$. Geometry: Pyramidal.
3. $IBr_2^-$: $I$ has 7 valence electrons + 1 (charge) $= 8$. 2 Bond pairs, 3 Lone pairs. Steric number $= 5$ ($sp^3d$). Geometry: Linear.
Thus, Statement II is True.
Step 3: Final Answer:
Statement I is false but Statement II is true.