PYQSide ExamsMy practice

Chemical Bonding and Molecular Structure · Question 89

AIPMT 2006MCQMedium📈 Topic in 12% papers+4−1
1

The electronegativity difference between N and F is greater than that between N and H yet the dipole moment of NH3 (1.5 D) is larger than that of NF3 (0.2 D). This is because

  1. in NH3 the atomic dipole and bond dipole are in the opposite directions whereas in NF3 these are in the same direction
  2. in NH3 as well as in NF3 the atomic dipole and bond dipole are in the same direction
  3. in NH3 the atomic dipole and bond dipole are in the same direction whereas in NF3 these are in opposite directions
  4. in NH3 as well as in NF3 the atomic dipole and bond dipole are in opposite directions.

Answer

(3) in NH3 the atomic dipole and bond dipole are in the same direction whereas in NF3 these are in opposite directions

Solution

Both NH3 and NF3 are pyramidal with one lone pair on N; the lone pair gives an orbital (atomic) dipole pointing away from N towards the lone pair.

In NH3: N is more electronegative than H, so each N–H bond dipole points towards N, i.e. the resultant of the bond dipoles points in the same direction as the lone-pair dipole.

⇒ The two add up ∴ large dipole moment (1.5 D).

In NF3: F is more electronegative than N, so each N–F bond dipole points away from N towards F, opposite to the lone-pair dipole.

⇒ They partly cancel ∴ small dipole moment (0.2 D).

As per NCERT, the orbital dipole due to the lone pair is in the same direction as the resultant dipole of the N–H bonds in NH3, but opposite to the resultant dipole of the three N–F bonds in NF3.

Answer: (3)

AIPMT 2006

Keep practising — Chemical Bonding and Molecular Structure

2

In which of the following molecules are all the bonds not equal?

  1. NF3
  2. ClF3
  3. BF3
  4. AlF3
AIPMT 2006
3

Which of the following molecules has trigonal planar geometry?

  1. BF3
  2. NH3
  3. PCl3
  4. IF3
AIPMT 2005
4

The correct order in which the O-O bond length increases in the following is

  1. O2 < H2O2 < O3
  2. O3 < H2O2 < O2
  3. H2O2 < O2 < O3
  4. O2 < O3 < H2O2
AIPMT 2005
5

The correct sequence of increasing covalent character is represented by

  1. LiCl < NaCl < BeCl2
  2. BeCl2 < LiCl < NaCl
  3. NaCl < LiCl < BeCl2
  4. BeCl2 < NaCl < LiCl
AIPMT 2005
6

Which of the following would have a permanent dipole moment?

  1. SiF4
  2. SF4
  3. XeF4
  4. BF3
AIPMT 2005
7

Among the following, the pair in which the two species are not isostructural is

  1. SiF4 and SF4
  2. IO3- and XeO3
  3. BH4- and NH4+
  4. PF6- and SF6
AIPMT 2004
8

In a regular octahedral molecule, MX6, the number of X - M - X bonds at 180 is

  1. three
  2. two
  3. six
  4. four
AIPMT 2004
9

H2O is dipolar, whereas BeF2 is not. It is because

  1. the electronegativity of F is greater than that of O
  2. H2O involves hydrogen bonding whereas BeF2 is a discrete molecule
  3. H2O is linear and BeF2 is angular
  4. H2O is angular and BeF2 is linear.
AIPMT 2004
10

In BrF3 molecule, the lone pairs occupy equatorial positions to minimize

  1. lone pair - bond pair repulsion only
  2. bond pair - bond pair repulsion only
  3. lone pair - lone pair repulsion and lone pair - bond pair repulsion
  4. lone pair - lone pair repulsion only.
AIPMT 2004
11

Which one of the following statements is not correct for sigma- and pi- bonds formed between two carbon atoms?

  1. sigma-bond is stronger than a pi-bond.
  2. Bond energies of sigma- and pi-bonds are of the order of 264 kJ/mol and 347 kJ/mol, respectively
  3. Free rotation of atoms about a sigma-bond is allowed but not in case of a pi-bond.
  4. Sigma-bond determines the direction between carbon atoms but a pi-bond has no primary effect in this regard.
AIPMT 2003

All Chemical Bonding and Molecular Structure PYQs →

PDFDownload Chemical Bonding and Molecular Structure PYQs as PDF Free, with answer key and a QR code to every solution — print it or study offline⬇
All NEET Chemistry chapters
Physical ChemistrySome Basic Concepts of ChemistryStructure of AtomStates of MatterThermodynamicsEquilibriumRedox ReactionsSolid StateSolutionsElectrochemistryChemical KineticsSurface Chemistry
Inorganic ChemistryClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular StructureHydrogens-Block Elementsp-Block Elements (Group 13 & 14)Environmental ChemistryGeneral Principles of Isolation of Elementsp-Block Elements (Group 15–18)d- and f-Block ElementsCoordination Compounds
Organic ChemistryOrganic Chemistry – Some Basic Principles and TechniquesIsomerismHydrocarbonsHaloalkanes and HaloarenesAlcohols, Phenols and EthersAldehydes, Ketones and Carboxylic AcidsAminesBiomoleculesPolymersChemistry in Everyday LifePrinciples Related to Practical Chemistry