Aqueous ammonia is used as a precipitating reagent for ${\rm{A}}{{\rm{l}}^{3 + }}$ ions as ${\rm{AI}}{\left( {{\rm{OH}}} \right)_3}$ rather than aqueous NaOH, because:

NaOH forms ${\left[ {{\rm{Al}}{{\left( {{\rm{OH}}} \right)}_4}} \right]^ - }$ ions

${\rm{NH}}_4^ + $ is a weak base

NaOH forms ${\left[ {{\rm{Al}}{{\left( {{\rm{OH}}} \right)}_2}} \right]^ + }$ ions

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JEE • CHEMISTRY • 13 TH GROUP ELEMENTS (P-BLOCK)

13 th group elements (p-block) practice · Medium

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Showing 1-30 of 98 questions

1 Medium

1 of 98

Remembering +4 | -1

Duralumin is an alloy of:

View answer and explanation

Correct option: C

Al, Mg, Mn and Cu

Option C (Al, Mg, Mn and Cu) is correct because Duralumin is an alloy primarily composed of aluminium, with smaller amounts of magnesium, manganese, and copper to enhance its strength and hardness.

2 Medium

2 of 98

Understanding +4 | -1

Consider the following statements about boric acid.

I. It is a weak monobasic acid

II. It is not a protonic acid

III. It acts as a lewis acid

The correct statement(s) among the following is/are

View answer and explanation

Correct option: D

I, II and III

Option D (I, II and III) is correct because boric acid is a weak monobasic acid, it is not a protonic acid, and it acts as a Lewis acid.

3 Medium

3 of 98

Analyzing +4 | -1

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}

\left[{Al}\left({H}_2{O}\right)_6\right]^{3+}

ion is

\mathrm{sp}^3 \mathrm{d}^2

Choose the correct answer from the options given below:

View answer and explanation

Correct option: A

Option A ((C) and (E) only) is correct because only statements C and E are factually accurate regarding the properties of group 13 elements.

4 Medium

4 of 98

Remembering +4 | -1

The 13th group element which has the least melting point is

View answer and explanation

Correct option: C

Option C (Ga) is correct because Gallium has an unusually low melting point compared to other group 13 elements.

5 Medium

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Understanding +4 | -1

Assertion (A) :

\mathrm{B}_3 \mathrm{N}_3 \mathrm{H}_{12}

(similar to cyclohexane) exists as chair conformation.

Reason (R) : Borazine

\left(\mathrm{B}_3 \mathrm{N}_3 \mathrm{H}_6\right)

is much more reactive than benzene.

View answer and explanation

Correct option: B

Both

\mathbf{A}

and

\mathbf{R}

are true but

\mathbf{R}

is not the correct explanation of

\mathbf{A}

Option B is correct because both the assertion and the reason are true, but the reason does not explain the assertion. The chair conformation of B3N3H12 is due to its structure, and the reactivity of borazine is a separate fact.

6 Medium

6 of 98

Understanding +4 | -1

Aluminium utensils should not be washed with materials containing washing soda because:

View answer and explanation

Correct option: C

Of reaction of washing soda with Aluminium to form soluble aluminate

Option C is correct because washing soda (sodium carbonate) reacts with aluminum to form soluble aluminates, which corrode the aluminum utensils.

7 Medium

7 of 98

Analyzing +4 | -1

Statement-I: The first ionisation energy of

{Al}

is lower than magnesium.

Statement-II: Atomic radius of

{Al}

is smaller than magnesium.

View answer and explanation

Correct option: A

Statement I and Statement II both are correct

Option A is correct. The first ionization energy of Al is lower than Mg due to Mg having a fully filled s-orbital, and the atomic radius of Al is indeed smaller than Mg due to increased nuclear charge.

8 Medium

8 of 98

Analyzing +4 | -1

Assertion: Electronegativity first increases from B to Al and then decreases from Al to

\mathrm{TI}

.

Reason: Due to poor shielding by inner

\mathrm{d}

and

\mathrm{f}

electrons.

View answer and explanation

Correct option: D

Assertion is false, but Reason is true

Option D (Assertion is false, but Reason is true) is correct because electronegativity decreases from B to Al, then increases from Al to Tl due to poor shielding by inner d and f electrons.

9 Medium

9 of 98

Understanding +4 | -1

In the reaction

\mathrm{B}(\mathrm{OH})_3+2 \mathrm{H}_2 \mathrm{O} \rightarrow\left[\mathrm{B}(\mathrm{OH})_4\right]^{-}+\mathrm{H}_3 \mathrm{O}^{+}. \mathrm{B}(\mathrm{OH})_3

functions as:

View answer and explanation

Correct option: D

Lewis acid

Option D (Lewis acid) is correct because

B(OH)_3

accepts electrons from water to form

[B(OH)_4]^-

and

H_3O^+

, acting as a Lewis acid.

10 Medium

10 of 98

Remembering +4 | -1

The form of BN which is an hard as diamond is

View answer and explanation

Correct option: A

Cubic form with ZnS structure

Option A (Cubic form with ZnS structure) is correct because the cubic form of Boron Nitride (BN) with a Zinc blende (ZnS) structure is known to be as hard as diamond.

11 Medium

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Understanding +4 | -1

Assertion (A): Borazine is more reactive than benzene.

Reason (R): Borazine is isostructural with benzene.

View answer and explanation

Correct option: B

Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

Option B (Both (A) & (R) are true but the (R) is not the correct explanation of the (A)) is correct because borazine is more reactive due to polarity, not its structure.

12 Medium

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Analyzing +4 | -1

(A): Among IIIA group gallium has low melting point.

(R): Gallium has

4 s^2 4 p^1

configuration in the valence shell.

View answer and explanation

Correct option: B

Both (A) and (R) are true and (R) is not the correct explanation of (A)

Option B (Both (A) and (R) are true and (R) is not the correct explanation of (A)) is correct because gallium does have a low melting point, and it has the given electronic configuration, but the electronic configuration is not the direct reason for the low melting point.

13 Medium

13 of 98

Understanding +4 | -1

Reaction of diborane with ammonia gives initially

View answer and explanation

Correct option: D

\left[{BH}_2\left({NH}_3\right)_2\right]^{+}\left[{BH}_4\right]^{-}

Option D (

\left[{BH}_2\left({NH}_3\right)_2\right]^{+}\left[{BH}_4\right]^{-}

) is correct because diborane reacts with ammonia to initially form diammoniate of diborane, which exists as an ionic compound.

14 Medium

14 of 98

Understanding +4 | -1

Aqueous ammonia is used as a precipitating reagent for

\mathrm{A}{\mathrm{l}^{3 + }}

ions as

\mathrm{AI}{\left( {\mathrm{OH}} \right)_3}

rather than aqueous NaOH, because:

View answer and explanation

Correct option: C

NaOH forms

{\left[ {\mathrm{Al}{{\left( {\mathrm{OH}} \right)}_4}} \right]^ - }

ions

Option C (NaOH forms

{\left[ {\mathrm{Al}{{\left( {\mathrm{OH}} \right)}_4}} \right]^ - }

ions) is correct because NaOH can dissolve

Al(OH)_3

forming a soluble complex, while ammonia does not.

15 Medium

15 of 98

Analyzing +4 | -1

For compound having the formula

GaAICI_4

, the correct option from the following is

View answer and explanation

Correct option: B

Ga

is more electronegative than

AI

and is present as a cationic part of the salt

GaAICI_4

The correct answer is D because the oxidation state of Ga in the salt GaAlCl4 is +1, not +3, as it exists as Ga+ [AlCl4]-.

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16 Medium

16 of 98

Understanding +4 | -1

Assertion (A): The group BN is isoelectronic with

\mathrm{C}_2

.

Reason (R) : No species containing a

B=N

group has yet been discovered.

View answer and explanation

Correct option: B

Both

\mathbf{A}

and

\mathbf{R}

are true but

\mathbf{R}

is not the correct explanation of

\mathbf{A}

The correct answer is B (ethylacetylene and but-1-yne) because the common name is ethylacetylene and the IUPAC name is but-1-yne.

17 Medium

17 of 98

Understanding +4 | -1

Alumina may be converted into anhydrous aluminium chloride by:

View answer and explanation

Correct option: D

Mixing it with carbon and heating the mixture in a current of dry chlorine

Option D (Mixing it with carbon and heating the mixture in a current of dry chlorine) is correct because carbon acts as a reducing agent, and chlorine converts the aluminum to aluminum chloride.

18 Medium

18 of 98

Remembering +4 | -1

What is the colour obtained when borax is heated in a Bunsen burner flame with

{CoO}

View answer and explanation

Correct option: A

Blue

Option A (Blue) is correct because cobalt oxide (CoO) reacts with borax to form cobalt metaborate (

Co(BO_2)_2

), which imparts a blue color to the bead.

19 Medium

19 of 98

Understanding +4 | -1

Which of the following oxide is of acidic nature?

View answer and explanation

Correct option: A

{B}_2 {O}_3

Option A (

{B}_2 {O}_3

) is correct because boron oxide is acidic due to the small size of boron, as explained by Fajan's rule.

20 Medium

20 of 98

Remembering +4 | -1

Which of the following is pseudoalum?

View answer and explanation

Correct option: C

\mathrm{MnS}{\mathrm{O}_4} \cdot \mathrm{A}{\mathrm{l}_2}{\left( {\mathrm{S}{\mathrm{O}_4}} \right)_3} \cdot 24{\mathrm{H}_2}\mathrm{O}

Option C (

\mathrm{MnS}{\mathrm{O}_4} \cdot \mathrm{A}{\mathrm{l}_2}{\left( {\mathrm{S}{\mathrm{O}_4}} \right)_3} \cdot 24{\mathrm{H}_2}\mathrm{O}

) is correct because a pseudoalum has a divalent cation (like Mn²⁺) in place of the monovalent cation.

21 Medium

21 of 98

Remembering +4 | -1

Amphoteric hydroxide from the following is

View answer and explanation

Correct option: A

{Al}({OH})_3

Option A (

{Al}({OH})_3

) is correct because aluminum hydroxide is amphoteric, meaning it can react with both acids and bases.

22 Medium

22 of 98

Understanding +4 | -1

Taking stability as the factor, which one of the following represents correct relationship?

View answer and explanation

Correct option: B

\text{TlI} > \text{T}\ell\text{I}_3

Option B (

\text{TlI} > \text{T}\ell\text{I}_3

) is correct because thallium(I) iodide is more stable than thallium(III) iodide due to the inert pair effect.

23 Medium

23 of 98

Understanding +4 | -1

Aluminium chloride exists as dimer,

\mathrm{A}{\mathrm{l}_2}\mathrm{C}{\mathrm{l}_6}

, in solid state as well as in solution of non-polar solvents such as benzene. When dissolved in water, it gives

View answer and explanation

Correct option: B

{\left[ {\mathrm{Al}{{\left( {{\mathrm{H}_2}\mathrm{O}} \right)}_6}} \right]^{3 + }} + 3\mathrm{C}{\mathrm{l}^ - }

Option B is correct because in water, aluminum chloride undergoes hydrolysis to form the hexaaquaaluminum(III) ion,

{\left[ {\mathrm{Al}{{\left( {{\mathrm{H}_2}\mathrm{O}} \right)}_6}} \right]^{3 + }}

, and chloride ions.

24 Medium

24 of 98

Understanding +4 | -1

The correct order of the first ionization enthalpy is

View answer and explanation

Correct option: D

\mathrm{Tl} > \mathrm{Ga} > \mathrm{Al}

Option C (

\mathrm{B} > \mathrm{Al} > \mathrm{Ga}

) is correct because ionization enthalpy generally decreases down a group, but Aluminum has a lower ionization enthalpy than Boron and Gallium due to electronic configuration and shielding effects.

25 Medium

25 of 98

Remembering +4 | -1

In group-13, thallium shows +1 oxidation state, while other members show +3 oxidation state, this is due to

View answer and explanation

Correct option: C

Inert pair effect

Option C (Inert pair effect) is correct because the inert pair effect causes the +1 oxidation state to be more stable than the +3 oxidation state for heavier elements like thallium in group 13.

26 Medium

26 of 98

Understanding +4 | -1

Potash alum is water soluble and ionises in aqueous solution to give:

View answer and explanation

Correct option: C

Three types of ions

Option D (Four types of ions) is correct because Potash alum,

KAl(SO_4)_2 \cdot 12H_2O

, dissociates into

K^+

Al^{3+}

, and

SO_4^{2-}

ions in water.

27 Medium

27 of 98

Remembering +4 | -1

Given below are two statements:

Statement I: The boron-10

\left({ }^{10} \mathrm{~B}\right)

isotope has high ability to absorb neutrons.

Statement II: On a weight-to-weight basis, the electrical conductivity of 'Al' is twice that of 'Cu'.

In the light of the above statements, choose the most appropriate answer from the options given below:

View answer and explanation

Correct option: D

Both Statement I and Statement II are correct

Option D (Both Statement I and Statement II are correct) is correct because Boron-10 is used in nuclear reactors due to its neutron absorption ability, and Aluminum has higher conductivity per weight than Copper.

28 Medium

28 of 98

Remembering +4 | -1

Which is not an alloy of aluminium?

View answer and explanation

Correct option: C

German silver

Option C (German silver) is correct because German silver is an alloy of copper, zinc, and nickel, not aluminum.

29 Medium

29 of 98

Understanding +4 | -1

Which of the following is correct statement?

View answer and explanation

Correct option: A

Aluminium dissolves in dilute mineral acids but is made passive by concentrated nitric acid

Option A (Aluminium dissolves in dilute mineral acids but is made passive by concentrated nitric acid) is correct because concentrated nitric acid forms a protective oxide layer on aluminum, preventing further reaction.

30 Medium

30 of 98

Understanding +4 | -1

In the following

\underset{(p)}{\left[{Al}\left({H}_2 {O}\right)_6\right]^{3+}}+\underset{(q)}{{HCO}_3^{-}} \Leftrightarrow \underset{(r)}{\left[{Al}\left({H}_2 {O}\right)_5 {OH}\right]^{2+}}+\underset{(s)}{{H}_2 {CO}_3}

species behaving as Brosnted-Lowry acids are

View answer and explanation

Correct option: A

(p), (s)

Option A (

(p), (s)

) is correct because in the forward reaction,

[{Al}({H}_2 {O})_6]^{3+}

donates a proton, and in the reverse reaction,

{H}_2 {CO}_3

donates a proton, thus acting as Bronsted-Lowry acids.

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Key Takeaways

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