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 · Mixed difficulty

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These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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Showing 1-30 of 163 questions

1 Medium

1 of 163

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 Hard

2 of 163

Analyzing +4 | -1

Assertion (A) : In aqueous solution

{AlCl}_3

forms dimer

{Al}_2 {Cl}_6

.
Reason (R) : The high enthalpy of hydration is sufficient to break the covalent dimer into

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

and

{Cl}^{-}

ions.

View answer and explanation

Correct option: D

\mathbf{A}

is false but

\mathbf{R}

is true.

Option D is correct. Assertion (A) is false because

{AlCl}_3

exists as a dimer in the gaseous phase and in non-polar solvents, but it ionizes in aqueous solution. Reason (R) is true because the high enthalpy of hydration favors ionization.

3 Easy

3 of 163

Remembering +4 | -1

{Al}_2\left({SO}_4\right)_3

is used in the following but not

View answer and explanation

Correct option: B

In plastic industry

Correct Answer + Core Reason: Option B (In leather industry) is the correct answer because

Al_2(SO_4)_3

is not primarily used in the leather industry.

4 Easy

4 of 163

Remembering +4 | -1

Which metal will give blue colour metaborate in borax bead test?

View answer and explanation

Correct option: A

{Cu}

Option A (

{Cu}

) is correct because copper gives a blue color in the borax bead test due to the formation of copper(II) metaborate.

5 Medium

5 of 163

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.

6 Medium

6 of 163

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.

7 Easy

7 of 163

Remembering +4 | -1

Which of the following is called alum?

View answer and explanation

Correct option: B

\mathrm{N}{\mathrm{a}_2}\mathrm{S}{\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 B (

\mathrm{N}{\mathrm{a}_2}\mathrm{S}{\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 it matches the general formula of alum, which is a double sulfate salt with the formula

{M'_2}\mathrm{S}{\mathrm{O}_4} \cdot {M'''_2}{\left( {\mathrm{S}{\mathrm{O}_4}} \right)_3} \cdot 24{\mathrm{H}_2}\mathrm{O}

8 Easy

8 of 163

Understanding +4 | -1

Statement-I: Borazole is inorganic benzene.

Statement-II: Benzene and Borazole are isoelectronic and show structural similarity.

View answer and explanation

Correct option: A

Both I and II are correct

Option A (Both I and II are correct) is correct because borazole (

B_3N_3H_6

) is indeed known as inorganic benzene due to its structural similarity and isoelectronic nature with benzene (

C_6H_6

9 Medium

9 of 163

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.

10 Easy

10 of 163

Remembering +4 | -1

In diborane, the banana bond is formed between

View answer and explanation

Correct option: A

2 electrons, 3 atoms

Option A (2 electrons, 3 atoms) is correct because the banana bond in diborane involves a 3-center-2-electron bond (B-H-B).

11 Medium

11 of 163

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.

12 Easy

12 of 163

Understanding +4 | -1

Stable compounds in +1 oxidation state are formed by:

View answer and explanation

Correct option: D

Option D (Tl) is correct because thallium exhibits a stable +1 oxidation state due to the inert pair effect.

13 Easy

13 of 163

Remembering +4 | -1

Borazole is obtained by reacting

{B_2}{H_6}

with

View answer and explanation

Correct option: A

N{H_3}

in the ratio

1:2

Option A (

N{H_3}

in the ratio

1:2

) is correct because borazole is formed by reacting diborane (

{B_2}{H_6}

) with ammonia (

N{H_3}

) in a 1:2 ratio.

14 Medium

14 of 163

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.

15 Medium

15 of 163

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.

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16 Medium

16 of 163

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.

17 Medium

17 of 163

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.

18 Medium

18 of 163

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.

19 Medium

19 of 163

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.

20 Medium

20 of 163

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.

21 Medium

21 of 163

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.

22 Medium

22 of 163

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.

23 Medium

23 of 163

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]-.

24 Easy

24 of 163

Remembering +4 | -1

Borax glass of a mixture of

View answer and explanation

Correct option: A

NaB{O_2} + {B_2}{O_3}\,

Option A (

NaB{O_2} + {B_2}{O_3}\,

) is correct because borax glass is a mixture of sodium metaborate and boron trioxide.

25 Medium

25 of 163

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.

26 Easy

26 of 163

Understanding +4 | -1

Assertion (A): Boron always forms covalent bond.

Reason (R) : The small size of

\mathrm{B}^{3+}

favours formation of covalent bond.

View answer and explanation

Correct option: A

Both

\mathbf{A}

and

\mathbf{R}

are true and

\mathbf{R}

is the correct explanation of

\mathbf{A}

Option A (Both

\mathbf{A}

and

\mathbf{R}

are true and

\mathbf{R}

is the correct explanation of

\mathbf{A}

) is correct because Boron's small size and high charge density favor covalent bond formation, as explained by the reason.

27 Medium

27 of 163

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.

28 Easy

28 of 163

Remembering +4 | -1

Which is amphoteric compound?

View answer and explanation

Correct option: C

\mathrm{A}{\mathrm{l}_2}{\mathrm{O}_3}

Option C (Al₂O₃) is correct because aluminum oxide (Al₂O₃) can react with both acids and bases, exhibiting amphoteric behavior.

29 Medium

29 of 163

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.

30 Easy

30 of 163

Understanding +4 | -1

Due to inert pair effect in 13th group

View answer and explanation

Correct option: B

Tl shows +1 oxidation state

Option A (

{E}_{({H})}>{E}_{({Li})}>{E}_{({Na})}>{E}_{({K})}

) is correct because ionization potential decreases down the group due to increasing atomic size and decreasing effective nuclear charge, and hydrogen has the highest ionization potential.

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Key Takeaways

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