Chemical Bonding -

1. A molecule has four electron domains around the central atom: three bond pair and one
lone pair. Which description is correct?

A. Electron-pair geometry tetrahedral; molecular geometry tetrahedral
B. Electron-pair geometry tetrahedral; molecular geometry trigonal pyramidal
C. Electron-pair geometry trigonal planar; molecular geometry trigonal pyramidal
D. Electron-pair geometry trigonal planar; molecular geometry trigonal planar

Answer

Option A Explained
Option A is correct. Carbon dioxide (CO₂) is linear, about 180°. Boron Trifluoride (BF₃) is trigonal planar, about 120°. Ammonia (NH₃) is trigonal pyramidal, about 107°. Water (H₂O) is bent with two lone pairs, about 104.5°.
Option B Explained
This is correct. The central atom has steric number 4, so the electron-domain geometry is tetrahedral. With one lone pair and three bonded atoms, the molecular geometry is trigonal pyramidal.
Option C Explained
This confuses number of bonded atoms with number of electron domains. Three bonded atoms do not automatically mean trigonal planar electron geometry.
Option D Explained
This ignores the lone pair completely. The lone pair changes both the electron-domain count and the visible shape.

2. Which set of molecules follows the correct order of bond angle from largest to smallest based on VSEPR Theory ?

A. AX₂ > AX₃ > AX₄ > AX₂E₂
B. AX₃ > AX₂ > AX₄ > AX₂E₂
C. AX₂ > AX₄ > AX₃ > AX₂E₂
D. AX₄ > AX₃ > AX₂ > AX₂E₂

Answer

Option A Explained
Option A is correct
AX₂ (linear) = 180°
AX₃ (trigonal planar) = 120°
AX₄ (tetrahedral) = 109.5°
AX₂E₂ (bent) ≈104.5°
Option B Explained
This option places trigonal planar above linear.
This ignores the linear geometry of AX₂.
Option C Explained
Incorrectly places tetrahedral above trigonal planar.
Option D Explained
Places tetrahedral above linear, violating VSEPR shapes predictions.

3. A molecule AX₃ has three identical polar A–X bonds but no permanent dipole moment. Which shape best explains this?

A. Trigonal planar
B. Trigonal pyramidal
C. Distorted trigonal planar
D. Bent

Answer

Option A is Correct
In trigonal planar geometry, three identical bond dipoles arranged symmetrically cancel out each other, making it overall non-polar, like BCl₃.

4. A student predicts that CO₂ is tetrahedral because carbon forms two double bonds, giving four bonding electron pairs around carbon. What is the best correction?

A. CO₂ is tetrahedral because four electron pairs surround carbon.
B. CO₂ is bent because each double bond creates two repulsion directions.
C. CO₂ is linear because each double bond acts as one bond pair.
D. CO₂ is trigonal planar because carbon has one lone pair and two bond pairs.

Answer

Option C is Correct
Carbon has two electron pairs in CO₂, so the electron-pair geometry and molecular geometry are linear.

5. Three neutral triatomic molecules are studied.

X is linear.
Y is bent with a bond angle slightly less than 120°.
Z is bent with a bond angle close to 104.5°.

Which conclusion is most reasonable?

A. Correct because electron pairs alone determines molecular geometry.
B. Correct because lone pairs do not influence shape.
C. Incorrect because molecular geometry depends on positions of atoms, not just electron pairs.
D. Incorrect because AX₃E has trigonal planar electron geometry.

Answer

Option B is Correct
A bent angle slightly below 120° suggests trigonal planar electron-pair geometry with one lone pair and two bond pairs, e.g SO₂ .

6. A student states that AX₄ and AX₃E have identical molecular geometries because both contain four electron domains. Which statement best evaluates this claim?

Answer

Option C is Correct
AX₄ is tetrahedral, while AX₃E is trigonal pyramidal. The distinction arises because lone pairs are not considered in deciding shapes or molecules.

7. A molecule has four electron domains around the central atom: three bond pair and one
lone pair. Which description is correct?

A. Shape/molecular geometry changes from trigonal planar to trigonal pyramidal.
B. Molecular geometry changes from trigonal planar to tetrahedral.
C. Shape changes from tetrahedral to trigonal planar.
D. Molecular geometry remains unchanged.

Answer

Option A is Correct
AX₃ becomes AX₃E. Electron geometry becomes tetrahedral while molecular geometry becomes trigonal pyramidal.

8. Two molecules contain three identical bonds. Molecule P has zero dipole moment. Molecule Q has a measurable dipole moment. Which pair qualifies the above properties?

A. P=AX₃, Q=AX₃E
B. P=AX₃E, Q=AX₃
C. P=AX₂E, Q=AX₂E₂
D. P=AX₃E, Q=AX₄

Answer

Option A is Correct
AX₃, like BCl₃, is trigonal planar and nonpolar whereas AX₃E, like NH₃, is trigonal pyramidal and polar. This exactly explains the observation.

9. Four unknown molecules are reported:

W= AX₂, X=AX₃, Y=AX₃E, Z= AX₂E₂

Which one is true statement about the above four molecules?

A. Z possesses a larger bond angle than X.
B. X is nonpolar.
C. Y possesses a smaller bond angle than Z.
D. W possesses the largest bond angle.

Answer

Option D is Correct
AX₂ is linear (180°). Among the listed geometries, no bond angle can exceed 180°. Therefore, W must possess the largest bond angle.

10. A researcher observes a molecule with:

Four non-identical bonds
Non-zero dipole moment
Bond angle nearly 109.5°

Based on the given properties, identify the most probable VSEPR type of the molecule.

A. AX₃E
B. AX₄
C. AX₂E₂
D. AX₃

Answer

Option B is Correct
The AX₄ molecule is tetrahedral, asymmetric, polar, and has nearly 109.5° bond angles.

11. A molecule has five bonding pairs around the central atom and no lone pairs. Which set of bond angles is expected?

A. 109.5° only
B. 90° and 180° only
C. 90°, 120°, and 180°
D. 120° only

Answer

Option C is Correct
AX₅ is trigonal bipyramidal. It has 120° between equatorial bonds, 90° between axial and equatorial bonds, and 180° between the two axial bonds.

12. A student says: “AX₅ and AX₆ molecules both contain only bond pairs, so they must have the same bond angles.” Which statement is correct?

A. Correct because all molecules without lone pairs have the same bond angles.
B. Incorrect because molecule with different bond pairs must have different bond angles
C. Correct; both have only 90° and 180° angles.
D. Incorrect; AX₅ is trigonal pyramidal and AX₆ is tetrahedral.

Answer

Option B is Correct
The molecule AX₅ is trigonal bipyramidal having five bond pairs while the molecule AX₆ is octahedral with six bond pairs. This is why AX₅ has different angles, i.e 90°, 120°, and 180° angles whereas AX₆ is octahedral with 90° and 180° angles. It means the angle 120^o is missing in octahedral.

13. Which of the following sets of molecules have a common angle present in all molecules?

A. PCl₅, NH₃, SF₆
B. SF₆, BeCl_2, NH₃
C. SeF₆, H₂O, SnCl₂
D. SF₆, PCl₅, CO₂

Answer

Option D is Correct
SF₆ (AX₆) contains 90° and 180° angles.
PCl₅ (AX₅) contains 90°, 120°, and 180° angles.
CO₂ (AX₂) contains a 180° bond angle.
Therefore, 180° is present in all three molecules, making this the only correct option.

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