Q55
jee_main_2026_21_jan_morning
Group 13 and 14 Compounds
Given below are two statements :
Statement I : The number of pairs among [SiO_2, CO_2]$[SiO_{2}, CO_{2}]$, [SnO, SnO_2]$[SnO, SnO_{2}]$, [PbO, PbO_2]$[PbO, PbO_{2}]$ and [GeO, GeO_2]$[GeO, GeO_{2}]$, which contain oxides that are both amphoteric is 2.
Statement II : BF_3$BF_{3}$ is an electron deficient molecule can act as a lewis acid, forms adduct with NH_3$NH_{3}$ and has a trigonal planar geometry.
In the light of the above statement, choose the correct answer from the option given below.
- A. textBoth Statement I and Statement II are true.$\text{Both Statement I and Statement II are true.}$
- B. textBoth Statement I and Statement II are false.$\text{Both Statement I and Statement II are false.}$
- C. textStatement I is true but Statement II is false.$\text{Statement I is true but Statement II is false.}$
- D. textStatement I is false Statement II is true.$\text{Statement I is false Statement II is true.}$
Solution
### Core Logic
Evaluating Statement I:
- SiO_2$SiO_2$, CO_2$CO_2$, GeO$GeO$, GeO_2$GeO_2$ are acidic in nature.
- SnO$SnO$, SnO_2$SnO_2$, PbO$PbO$, PbO_2$PbO_2$ are amphoteric in nature.
Therefore, the pairs [SnO, SnO_2]$[SnO, SnO_2]$ and [PbO, PbO_2]$[PbO, PbO_2]$ contain oxides that are both amphoteric. Number of such pairs = 2. Statement I is True.
Evaluating Statement II:
- BF_3$BF_3$ has 6 electrons in the outermost shell of the central Boron atom. It is electron-deficient and acts as a Lewis acid.
- It accepts a lone pair from Lewis bases like NH_3$NH_3$ to form an adduct.
- In BF_3$BF_3$, Boron is sp^2$sp^2$ hybridized, resulting in a trigonal planar geometry. Statement II is True.
### Step 1: Conclusion
Both statements are factually correct.
### Pattern Recognition
Oxides of heavier Group 14 elements (Sn, Pb) are typically amphoteric in both their +2 and +4 oxidation states. BF_3$BF_3$ is the quintessential Lewis acid.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: p-Block Elements
Class 11 Chemistry: Chemical Bonding and Molecular Structure
Q40
jee_main_2025_02_april_evening
Group 16 Elements (Oxygen Family)
The nature of oxide (mathrmTeO_2)$(\mathrm{TeO}_2)$ and hydride (mathrmTeH_2)$(\mathrm{TeH}_2)$ formed by Te, respectively are:
- A. textOxidising and acidic$\text{Oxidising and acidic}$
- B. textReducing and basic$\text{Reducing and basic}$
- C. textReducing and acidic$\text{Reducing and acidic}$
- D. textOxidising and basic$\text{Oxidising and basic}$
Solution
### Related Formula
textBond Strength propto frac1textSize difference$$\text{Bond Strength} \propto \frac{1}{\text{Size difference}}$$
textAcidic Strength propto frac1textM-H Bond Dissociation Energy$$\text{Acidic Strength} \propto \frac{1}{\text{M-H Bond Dissociation Energy}}$$
### Core Logic
Let's analyze the properties of Tellurium compounds:
1. **Tellurium Dioxide** (mathrmTeO_2$\mathrm{TeO}_2$):
- Due to the **inert pair effect**, the +6$+6$ oxidation state of Tellurium is less stable, whereas its +4$+4$ state is relatively stable. However, in comparison to sulphur dioxide (which is a strong reducing agent), mathrmTeO_2$\mathrm{TeO}_2$ is oxidising because the lower oxidation states (like element Tellurium or +2$+2$) are chemically accessible. Thus, mathrmTeO_2$\mathrm{TeO}_2$ acts as an **oxidising agent**.
2. **Tellurium Hydride** (mathrmTeH_2$\mathrm{TeH}_2$):
- Tellurium is a very large atom. The orbital overlap between Tellurium and Hydrogen is extremely poor. Hence, the mathrmTe-H$\mathrm{Te-H}$ bond is very long and has very **low bond dissociation energy**.
- This allows mathrmTeH_2$\mathrm{TeH}_2$ to easily release mathrmH^+$\mathrm{H^+}$ in solution, making it highly **acidic**.
### Step 1: Final Verification
Therefore, the nature of mathrmTeO_2$\mathrm{TeO}_2$ is oxidising, and the nature of mathrmTeH_2$\mathrm{TeH}_2$ is acidic.
### Pattern Recognition
Periodic Trend: As we go down Group 16:
- Acidic strength of hydrides increases: mathrmH_2O < H_2S < H_2Se < H_2Te$\mathrm{H_2O < H_2S < H_2Se < H_2Te}$.
- Reducing character of hydrides also increases.
- Reducing power of dioxides decreases: mathrmSO_2$\mathrm{SO_2}$ (reducing) rightarrow mathrmTeO_2$\rightarrow \mathrm{TeO_2}$ (oxidising).
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Chemistry: p-Block Elements
Q43
jee_main_2025_03_april_evening
Periodic Trends in Group 13 Elements
The correct orders among the following are :
- Atomic radius: mathrmB < mathrmAl < mathrmGa < mathrmIn < mathrmTl$\mathrm{B} < \mathrm{Al} < \mathrm{Ga} < \mathrm{In} < \mathrm{Tl}$
- Electronegativity: mathrmAl < mathrmGa < mathrmIn < mathrmTl < mathrmB$\mathrm{Al} < \mathrm{Ga} < \mathrm{In} < \mathrm{Tl} < \mathrm{B}$
- Density: mathrmTl < mathrmIn < mathrmGa < mathrmAl < mathrmB$\mathrm{Tl} < \mathrm{In} < \mathrm{Ga} < \mathrm{Al} < \mathrm{B}$
- 1^mathrmst$1^{\mathrm{st}}$ Ionisation Energy: mathrmIn < mathrmAl < mathrmGa < mathrmTl < mathrmB$\mathrm{In} < \mathrm{Al} < \mathrm{Ga} < \mathrm{Tl} < \mathrm{B}$
Choose the correct answer from the options given below :
- A. B and D Only
- B. A and C Only
- C. C and D Only
- D. A and B Only
Solution
### Related Formula
Group 13 elements (mathrmB, mathrmAl, mathrmGa, mathrmIn, mathrmTl$\mathrm{B}, \mathrm{Al}, \mathrm{Ga}, \mathrm{In}, \mathrm{Tl}$) show highly anomalous periodic trends due to the intervention of filled d-orbitals (d-block contraction in mathrmGa$\mathrm{Ga}$) and f-orbitals (lanthanoid contraction in mathrmTl$\mathrm{Tl}$).
### Core Logic
Evaluate each specified trend against official physical constants:
- **Atomic radius**: Due to d-block contraction, gallium (mathrmGa$\mathrm{Ga}$) is smaller than aluminum (mathrmAl$\mathrm{Al}$):
textRadius (pm): mathrmB(88) < mathrmGa(135) < mathrmAl(143) < mathrmIn(167) < mathrmTl(170)$$\text{Radius (pm): } \mathrm{B}(88) < \mathrm{Ga}(135) < \mathrm{Al}(143) < \mathrm{In}(167) < \mathrm{Tl}(170)$$
Hence, the given order is *Incorrect*.
- **Electronegativity**: Electronegativity first decreases from mathrmB$\mathrm{B}$ to mathrmAl$\mathrm{Al}$, then increases down the group due to poor shielding of d and f electrons:
textElectronegativity: mathrmAl(1.5) < mathrmGa(1.6) < mathrmIn(1.7) < mathrmTl(1.8) < mathrmB(2.0)$$\text{Electronegativity: } \mathrm{Al}(1.5) < \mathrm{Ga}(1.6) < \mathrm{In}(1.7) < \mathrm{Tl}(1.8) < \mathrm{B}(2.0)$$
Hence, this order is *Correct*.
### Step 1: Analyze density and ionization energy trends
- **Density**: Increases down the group as atomic mass increases much faster than atomic volume:
textDensity (g/cm^3text): mathrmB(2.35) < mathrmAl(2.70) < mathrmGa(5.90) < mathrmIn(7.31) < mathrmTl(11.85)$$\text{Density (g/cm}^3\text{): } \mathrm{B}(2.35) < \mathrm{Al}(2.70) < \mathrm{Ga}(5.90) < \mathrm{In}(7.31) < \mathrm{Tl}(11.85)$$
Hence, the given order is *Incorrect* (it is completely reversed).
- **1^mathrmst$1^{\mathrm{st}}$ Ionisation Energy**: Shows an irregular trend due to ineffective shielding by d and f electrons:
textIE_1mathrm~(kJ/mol): mathrmIn(558) < mathrmAl(577) < mathrmGa(579) < mathrmTl(589) < mathrmB(801)$$\text{IE}_1\mathrm{~(kJ/mol): } \mathrm{In}(558) < \mathrm{Al}(577) < \mathrm{Ga}(579) < \mathrm{Tl}(589) < \mathrm{B}(801)$$
Hence, this order is *Correct*.
### Step 2: Conclusion
Only the Electronegativity (B) and 1^mathrmst$1^{\mathrm{st}}$ Ionisation Energy (D) orders are correct, matching Option (1).
### Pattern Recognition
Group 13 elements do not follow monotonic trends. The poor shielding of 3d^10$3d^{10}$ and 4f^14$4f^{14}$ electrons increases the effective nuclear charge on valence electrons, causing anomalies in atomic radius (mathrmGa < mathrmAl$\mathrm{Ga} < \mathrm{Al}$) and pulling electronegativities and ionization energies upward as you go further down.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: The p-Block Elements
Class 11 Chemistry: Classification of Elements and Periodicity in Properties
Q38
jee_main_2025_07_april_morning
Properties of Group 14 Elements
The group 14 elements A and B have the first ionisation enthalpy values of 708 and 715mathrm\ kJ\ mol^-1$715\mathrm{\ kJ\ mol}^{-1}$ respectively. The above values are lowest among their group members. The nature of their ions mathrmA^2+$\mathrm{A}^{2+}$, mathrmB^4+$\mathrm{B}^{4+}$ respectively is:
- A. textboth reducing$\text{both reducing}$
- B. textboth oxidising$\text{both oxidising}$
- C. textreducing and oxidising$\text{reducing and oxidising}$
- D. textoxidising and reducing$\text{oxidising and reducing}$
Solution
### Core Logic
For Group 14 (textC, textSi, textGe, textSn, textPb$\text{C}, \text{Si}, \text{Ge}, \text{Sn}, \text{Pb}$):
- The ionisation energies generally decrease down the group, but there is an anomaly between textSn$\text{Sn}$ and textPb$\text{Pb}$ due to relativistic contraction / poor shielding of 4f electrons in textPb$\text{Pb}$.
- Thus, the first ionisation enthalpy of Tin (mathrmSn$\mathrm{Sn}$) is 708 text kJ mol^-1$708 \text{ kJ mol}^{-1}$ and Lead (mathrmPb$\mathrm{Pb}$) is 715 text kJ mol^-1$715 \text{ kJ mol}^{-1}$. These are indeed the lowest in the group.
- Hence, element **A** is mathrmSn$\mathrm{Sn}$ and **B** is mathrmPb$\mathrm{Pb}$.
Nature of their ions:
- mathrmA^2+ = mathrmSn^2+$\mathrm{A}^{2+} = \mathrm{Sn}^{2+}$: Since mathrmSn^4+$\mathrm{Sn}^{4+}$ is more stable than mathrmSn^2+$\mathrm{Sn}^{2+}$, mathrmSn^2+$\mathrm{Sn}^{2+}$ readily undergoes oxidation to +4$+4$, acting as a strong **reducing agent**.
- mathrmB^4+ = mathrmPb^4+$\mathrm{B}^{4+} = \mathrm{Pb}^{4+}$: Due to the strong **inert pair effect**, mathrmPb^2+$\mathrm{Pb}^{2+}$ is highly stable compared to mathrmPb^4+$\mathrm{Pb}^{4+}$. Thus, mathrmPb^4+$\mathrm{Pb}^{4+}$ is eager to reduce to +2$+2$, acting as a strong **oxidising agent**.
### Pattern Recognition
Inert pair effect becomes extremely prominent at the bottom of the group. Lead's most stable state is +2$+2$, making mathrmPb^4+$\mathrm{Pb}^{4+}$ oxidising. Tin's stable state is +4$+4$, making mathrmSn^2+$\mathrm{Sn}^{2+}$ reducing.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: p-Block Elements
Class 11 Chemistry: Periodic Classification of Elements
