Question

The correct statements from the following are:
(A) The decreasing order of atomic radii of group 13 elements is Tl $>$ In $>$ Ga $>$ Al $>$ B.
(B) Down the group 13 electronegativity decreases from top to bottom.
(C) Al dissolves in dil. HCl and liberate H$_2$, but conc. HNO$_3$ renders Al passive by forming a protective oxide layer on the surface.
(D) All elements of group 13 exhibits highly stable +1 oxidation state.
(E) Hybridisation of Al in [Al(H$_2$O)$_6$]$^{3+}$ ion is sp$^3$d$^2$.
Choose the correct answer from the options given below.

• A. (C) and (E) only
• B. (A), (C) and (E) only
• C. (A), (B), (C) and (E) only
• D. (A) and (C) only

Answer 1

The Correct Option is A

Step 1: Analyze each statement
Statement (A):
The correct order of atomic radii in group 13 elements is \(\text{Tl} > \text{In} > \text{Al} > \text{Ga} > \text{B}\), not \(\text{Tl} > \text{In} > \text{Ga} > \text{Al} > \text{B}\).  
- This statement is incorrect.
2.Statement (B):  
Down the group, electronegativity generally decreases. However, due to the presence of \(d\)-electrons in \(\text{Ga}\), \(\text{In}\), and \(\text{Tl}\), their electronegativity values do not follow a simple trend.  
- This statement is incorrect.
3.Statement (C):  
\(\text{Al}\) reacts with dilute \(\text{HCl}\) to release \(\text{H}_2\):
\[2\text{Al} + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2.\]
Concentrated \(\text{HNO}_3\) forms a passive oxide layer on \(\text{Al}\), protecting it from further reaction.  
- This statement is correct.
4.Statement (D):  
In group 13, the \(+3\) oxidation state is more stable than \(+1\). The \(+1\) state is exhibited by \(\text{Tl}\) due to the inert pair effect, but it is
not highly stable for all elements.  
- This statement is incorrect.
5.Statement (E):
In \([\text{Al}(\text{H}_2\text{O})_6]^{3+}\), the hybridization of \(\text{Al}\) is \(\text{sp}^3\text{d}^2\), corresponding to an octahedral geometry.  - This statement is correct.
Step 2: Conclusion
The correct statements are (C) and (E).
Final Answer: (1).

Answer 2

Step 1: Analyze statement (A).
Statement (A): The decreasing order of atomic radii of group 13 elements is Tl > In > Ga > Al > B.
This order is correct because the atomic size generally increases down the group, but due to d- and f-block contraction, Ga has a smaller atomic radius than Al. Hence, the correct trend is:
B < Al < Ga < In < Tl.
Thus, statement (A) is incorrect.

Step 2: Analyze statement (B).
Statement (B): Down the group 13, electronegativity decreases from top to bottom.
This is not entirely true because the electronegativity remains almost the same from Al to Tl due to the same contraction effect. Hence, statement (B) is incorrect.

Step 3: Analyze statement (C).
Statement (C): Al dissolves in dilute HCl and liberates H₂, but conc. HNO₃ renders Al passive by forming a protective oxide layer.
This statement is correct. Aluminum forms Al₂O₃ layer when treated with concentrated nitric acid, which prevents further reaction (passivation).

Step 4: Analyze statement (D).
Statement (D): All elements of group 13 exhibit a highly stable +1 oxidation state.
This is incorrect. The +1 oxidation state becomes more stable only for heavier elements (In and Tl) due to the inert pair effect. Lighter elements (B and Al) prefer the +3 state. Hence, (D) is incorrect.

Step 5: Analyze statement (E).
Statement (E): The hybridisation of Al in [Al(H₂O)₆]³⁺ is sp³d².
In this complex, aluminum forms six coordinate bonds with water molecules, giving an octahedral geometry. The hybridisation corresponding to octahedral geometry is sp³d². Hence, (E) is correct.

Step 6: Final Answer.
The correct statements are: (C) and (E) only.

Final Answer: (C) and (E) only