One mole of Cl2 (g) was passed into 2 L of cold 2M KOH solution. After the reaction, the concentrations of Cl-, ClO…

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Q68 jee_main_2024_01_february_morning Group 15 Elements

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) :

PH₃

has lower boiling point than

NH₃

. Reason (R): In liquid state

NH₃

molecules are associated through vander waal's forces, but

PH₃

molecules are associated through hydrogen bonding. In the light of the above statements, choose the most appropriate answer from the options given below:

A. $Both (A) and (R) are correct and (R) is not the correct explanation of (A)$
B. $(A) is not correct but (R) is correct$
C. $Both (A) and (R) are correct but (R) is the correct explanation of (A)$
D. $(A) is correct but (R) is not correct$

Solution

Core Logic

$NH₃$ $NH_3$ undergoes extensive intermolecular hydrogen bonding due to the high electronegativity and small size of Nitrogen. $PH₃$ $PH_3$ (Phosphine) molecules are only held together by weak van der Waals (dispersion) forces because Phosphorus is less electronegative and larger, unable to form strong hydrogen bonds.

Step 1: Evaluate Statements

Assertion (A) is correct: $PH₃$ $PH_3$ has a lower boiling point than $NH₃$ $NH_3$ because breaking H-bonds in $NH₃$ $NH_3$ requires more energy. Reason (R) is incorrect: It falsely claims $NH₃$ $NH_3$ has van der Waals association and $PH₃$ $PH_3$ has hydrogen bonding. It is exactly the opposite.

Pattern Recognition

N, O, and F are the only atoms electronegative enough to form stable hydrogen bonds in simple hydrides. Boiling point anomaly: $NH₃ > PH₃$ $NH_3 > PH_3$ purely due to H-bonding in $NH₃$ $NH_3$.

Chapter Mix

Class 12 Chemistry: The p-Block Elements Class 11 Chemistry: Chemical Bonding and Molecular Structure

Q jee_main_2024_29_january_evening Anomalous Behaviour of Oxygen

Anomalous behaviour of oxygen is due to its

A. Large size and high electronegativity
B. Small size and low electronegativity
C. Small size and high electronegativity
D. Large size and low electronegativity

Solution

Related Formula

Anomalous properties of second-period elements

Core Logic

The anomalous properties of oxygen compared to other chalcogens stem directly from its position in the second period of the periodic table. It is characterized by:

An exceptionally small atomic radius.
Highly pronounced electronegativity.
Complete absence of low-energy valence $d$ $d$-orbitals.

Step 1: Selection Verification

Therefore, the combination of small size and high electronegativity is the correct choice, matching option C.

Pattern Recognition

All first members of periodic blocks ( $N$ $\text{N}$, $O$ $\text{O}$, $F$ $\text{F}$) deviate significantly from their heavier group members due to their high charge density, high electronegativity, and lack of $d$ $d$-orbitals.

Chapter Mix

Class 11 Chemistry: p-Block Elements

Q73 jee_main_2024_27_jan_morning Properties of Boron

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Melting point of Boron (

2453 K

) is unusually high in group 13 elements. Reason (R) : Solid Boron has very strong crystalline lattice. In the light of the above statements, choose the most appropriate answer from the options given below;

A. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
B. Both (A) and (R) are correct and (R) is the correct explanation of (A)
C. (A) is true but (R) is false
D. (A) is false but (R) is true

Solution

Core Logic

Boron forms a highly compact, robust icosahedral covalent polymeric three-dimensional framework structure ( $B₁₂$ $B_{12}$ units). This extremely solid, dense crystalline lattice organization requires immense thermal activation energy to rupture, explaining why its melting point ( $2453 K$ $2453\text{ K}$) is uniquely elevated among Group 13 elements. Both statements are true and (R) is the perfect explanation.

Chapter Mix

Class 11 Chemistry: p-Block Elements

Q90 jee_main_2024_27_jan_morning Oxidation States of Sulphur

From the given list, the number of compounds with +4 oxidation state of Sulphur:

SO₃

,

H₂SO₃

,

SOCl₂

,

SF₄

,

BaSO₄

,

H₂S₂O₇

Numerical Answer. Answer: 3 to 3

Solution

Step 1: Audit oxidation numbers individually

Compound	Oxidation State of Sulphur Calculation
$SO₃$ $\text{SO}_3$	$x + 3(-2) = 0 x = +6$ $x + 3(-2) = 0 \implies x = +6$
$H₂SO₃$ $\text{H}_2\text{SO}_3$	$2(+1) + x + 3(-2) = 0 x = +4$ $2(+1) + x + 3(-2) = 0 \implies x = +4$
$SOCl₂$ $\text{SOCl}_2$	$x + (-2) + 2(-1) = 0 x = +4$ $x + (-2) + 2(-1) = 0 \implies x = +4$
$SF₄$ $\text{SF}_4$	$x + 4(-1) = 0 x = +4$ $x + 4(-1) = 0 \implies x = +4$
$BaSO₄$ $\text{BaSO}_4$	$+2 + x + 4(-2) = 0 x = +6$ $+2 + x + 4(-2) = 0 \implies x = +6$
$H₂S₂O₇$ $\text{H}_2\text{S}_2\text{O}_7$	$2(+1) + 2x + 7(-2) = 0 2x = 12 x = +6$

Step 2: Sum the targets

The compounds displaying an exact $+4$ $+4$ assignment are $H₂SO₃$ $\text{H}_2\text{SO}_3$, $SOCl₂$ $\text{SOCl}_2$, and $SF₄$ $\text{SF}_4$. The total number is 3.

Pattern Recognition

Sulfurous derivatives, thionyl groupings, and tetrafluoride configurations typically feature the $+4$ $+4$ oxidation level state.

Chapter Mix

Class 11 Chemistry: Redox Reactions Class 12 Chemistry: p-Block Elements

Q65 jee_main_2024_29_jan_morning Group 14 Elements Physical Properties

Given below are two statements : Statement I : The electronegativity of group 14 elements from Si to Pb gradually decreases. Statement II : Group 14 contains non-metallic, metallic, as well as metalloid elements. In the light of the above statements, choose the most appropriate from the options given below:

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

Solution

Core Logic

Analyzing Statement I: The electronegativity values for Group 14 elements according to the Pauling scale are approximately:

Carbon (C): $2.5$ $2.5$
Silicon (Si): $1.8$ $1.8$
Germanium (Ge): $1.8$ $1.8$
Tin (Sn): $1.8$ $1.8$
Lead (Pb): $1.9$ $1.9$

The electronegativity values from Si to Pb are almost identical, and it slightly increases at Pb due to the poor shielding effect of d and f-orbitals (inert pair effect). It does not "gradually decrease." Therefore, Statement I is false.

Analyzing Statement II: Group 14 consists of:

Carbon (C): Non-metal
Silicon (Si) & Germanium (Ge): Metalloids
Tin (Sn) & Lead (Pb): Metals

Therefore, the group contains non-metals, metalloids, and metals. Statement II is true.

Step 1: Final Conclusion

Statement I is false, but Statement II is true.

Pattern Recognition

Electronegativity in Group 13 and 14 does not follow a strict linear decrease due to d-block and f-block contraction (poor shielding by d and f electrons).

Chapter Mix

Class 11 Chemistry: The p Block Elements

One mole of Cl₂$Cl_{2}$ (g) was passed into 2 L of cold 2M KOH solution. After the reaction, the concentrations of Cl⁻$Cl^{-}$, ClO⁻$ClO^{-}$ and OH⁻$OH^{-}$ are respectively (assume volume remains constant)

Solution & Explanation

Core Logic

Step 1: Stoichiometry

Step 2: Final Concentrations

Pattern Recognition

Chapter Mix

Reference Study Guides

More The p-Block Elements Previous-Year Questions — Page 7

Solution

Core Logic

Step 1: Evaluate Statements

Pattern Recognition

Chapter Mix

Solution

Related Formula

Core Logic

Step 1: Selection Verification

Pattern Recognition

Chapter Mix

Solution

Core Logic

Chapter Mix

Solution

Step 1: Audit oxidation numbers individually

Step 2: Sum the targets

Pattern Recognition

Chapter Mix

Solution

Core Logic

Step 1: Final Conclusion

Pattern Recognition

Chapter Mix

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One mole of $Cl₂$ $Cl_{2}$ (g) was passed into 2 L of cold 2M KOH solution. After the reaction, the concentrations of $Cl⁻$ $Cl^{-}$, $ClO⁻$ $ClO^{-}$ and $OH⁻$ $OH^{-}$ are respectively (assume volume remains constant)