The molecule having pyramidal shape is
A BF₃
B NH₃
C CO₂
D BeCl₂
NH₃ has 3 bond pairs and 1 lone pair on N (AX₃E). Electron geometry is tetrahedral but molecular shape is trigonal pyramidal.
Which molecule is expected to have square pyramidal geometry
A SF₆
B BrF₅
C PF₅
D XeF₄
BrF₅ has 5 bond pairs + 1 lone pair (AX₅E) → octahedral electron geometry → square pyramidal molecular shape.
The hybridization of central atom in BrF₅ is
A sp³
B sp³d
C sp³d²
D dsp²
Total electron domains = 6 (5 bonds + 1 lone pair) → sp³d² hybridization.
Which molecule has trigonal bipyramidal electron geometry but seesaw shape
A PF₅
B SF₄
C XeF₄
D IF₇
SF₄ has 4 bond pairs + 1 lone pair (AX₄E). Electron geometry TBP; lone pair makes seesaw shape.
The number of lone pairs on the central atom in XeF₄ is
A 0
B 1
C 2
D 3
Xe has 8 valence electrons; XeF₄ uses 4 bond pairs, leaving 2 lone pairs (AX₄E₂).
The molecule with maximum bond angle among these is
A NH₃
B H₂O
C CH₄
D CO₂
CO₂ is linear (180°), larger than CH₄ (109.5°), NH₃ (~107°), H₂O (~104.5°).
The type of hybridization in acetylene (C₂H₂) is
A sp
B sp²
C sp³
D sp³d
Each C has two electron domains (one σ to H and one σ to C; π bonds separate) → sp, linear.
Which compound has the highest ionic character
A LiF
B LiCl
C LiBr
D LiI
Highest electronegativity difference and least polarizability of F⁻ → most ionic.
According to Fajan’s rule, covalent character increases when
A Anion is large and cation is large
B Anion is small and cation is small
C Cation is small with high charge and anion is large
D Both ions have low charge
Small highly charged cation strongly polarizes large anion → increased covalent character.
Which compound has the highest lattice energy
A NaCl
B KCl
C LiF
D CsI
Lattice energy increases with higher ionic charge and smaller ionic size. Li⁺ and F⁻ are small → strongest attraction.
The bond order of N₂⁺ is
A 2
B 2.5
C 3
D 3.5
N₂ has bond order 3. Removing one electron from a bonding MO decreases bond order by 0.5 → 2.5.
Which species is diamagnetic
A O₂
B O₂⁻
C O₂²⁻
D NO
O₂²⁻ (peroxide) has all electrons paired in MO configuration → diamagnetic.
The bond order of NO⁺ is
A 1.5
B 2
C 2.5
D 3
NO⁺ is isoelectronic with N₂ (14 electrons) → bond order 3.
Which is most paramagnetic (maximum unpaired electrons)
A O₂
B O₂⁺
C O₂⁻
D O₂²⁻
O₂ has two unpaired electrons; O₂⁺ and O₂⁻ have one unpaired; O₂²⁻ has none.
As bond order decreases, bond length generally
A decreases
B increases
C becomes zero
D remains constant
Lower bond order means weaker bond and larger internuclear distance → longer bond length.
The coordination number of Co in [Co(en)₂Cl₂]⁺ is
A 2
B 4
C 6
D 8
en is bidentate: 2 en ligands provide 4 donor sites + 2 Cl⁻ donor sites = 6.
The complex [Co(NH₃)₅Cl]Cl₂ gives how many ions in solution
A 1
B 2
C 3
D 4
It dissociates as [Co(NH₃)₅Cl]²⁺ + 2Cl⁻ → total 3 ions.
Which complex will give maximum ions in solution
A [Co(NH₃)₆]Cl₃
B [Co(NH₃)₅Cl]Cl₂
C [Co(NH₃)₄Cl₂]Cl
D [Co(NH₃)₃Cl₃]
Dissociation: [Co(NH₃)₆]³⁺ + 3Cl⁻ → 4 ions (maximum).
The complex [Pt(NH₃)₂Cl₂] exhibits which type of isomerism
A Linkage only
B Geometrical only
C Optical only
D Coordination only
Square planar MA₂B₂ complexes show cis/trans isomerism.
Which complex is chiral and shows optical isomerism
A [Co(NH₃)₆]³⁺
B [Cr(en)₃]³⁺
C [Pt(NH₃)₂Cl₂]
D [Ni(CO)₄]
Octahedral complexes with three bidentate ligands are chiral (Δ/Λ forms).
Which complex can show linkage isomerism
A [Co(NH₃)₅NO₂]²⁺
B [Co(NH₃)₆]³⁺
C [Zn(NH₃)₄]²⁺
D [Ni(CO)₄]
NO₂⁻ can coordinate through N (nitro) or O (nitrito) → linkage isomerism.
In the IUPAC name, ligands are arranged
A According to molecular mass
B According to increasing oxidation state
C Alphabetically (ignoring prefixes di-, tri-)
D Only by charge
Ligand names are written in alphabetical order, and multiplicative prefixes are not considered.
Oxidation state of Co in [Co(NH₃)₄Cl₂]Cl is
A +1
B +2
C +3
D +4
Outside Cl⁻ is −1, so complex cation is +1. Inside: 2Cl⁻ = −2, NH₃ neutral. Co −2 = +1 → Co = +3.
The IUPAC name of [Cr(H₂O)₆]Cl₃ is
A Hexaaquachromium(I) chloride
B Hexaaquachromium(III) chloride
C Trichloride hexaaquachromium
D Hexaaqua trichlorochromium
Complex is [Cr(H₂O)₆]³⁺, Cr oxidation state +3; counter ions are chloride.
The number of geometrical isomers possible for [Co(NH₃)₄Cl₂]⁺ is
A 1
B 2
C 3
D 4
Octahedral MA₄B₂ gives cis and trans → 2 geometrical isomers.
The number of geometrical isomers possible for [Co(NH₃)₃Cl₃] is
A 1
B 2
C 3
D 4
Octahedral MA₃B₃ shows fac and mer isomerism → 2.
Which complex shows fac–mer isomerism
A [Co(NH₃)₆]³⁺
B [Co(NH₃)₄Cl₂]⁺
C [Co(NH₃)₃Cl₃]
D [Pt(NH₃)₂Cl₂]
fac/mer isomerism is characteristic of octahedral MA₃B₃ type complexes.
In octahedral splitting, the lower energy set is
A e_g
B t₂g
C both equal
D none
In octahedral field, dxy, dyz, dxz (t₂g) are stabilized (lower) relative to eg.
In octahedral complexes, crystal field stabilization energy (CFSE) depends on
A Only oxidation state
B Only coordination number
C Distribution of electrons in t₂g and e_g
D Only type of geometry
CFSE arises due to how d-electrons occupy split orbitals.
Which ligand is weak field
A CN⁻
B CO
C NO₂⁻
D F⁻
F⁻ is a weak field ligand (small Δo) compared to CN⁻/CO (strong field).
High spin complex is favored when
A Δo is large
B Pairing energy is much smaller than Δo
C Δo is small
D Ligand is strong field
If splitting is small, electrons avoid pairing and occupy higher orbitals → high spin.
The magnetic moment (spin-only) depends on
A Number of paired electrons
B Number of unpaired electrons
C Atomic mass
D Coordination number only
Spin-only magnetic moment μ = √(n(n+2)) BM, where n = unpaired electrons.
For n = 4 unpaired electrons, spin-only magnetic moment is closest to
A 2.83 BM
B 3.87 BM
C 4.90 BM
D 5.92 BM
μ = √(n(n+2)) = √(4×6)=√24 ≈ 4.90 BM.
Which metal ion (free ion) has maximum unpaired electrons
A Fe²⁺ (d⁶)
B Mn²⁺ (d⁵)
C Co²⁺ (d⁷)
D Ni²⁺ (d⁸)
d⁵ in high spin has 5 unpaired electrons (maximum).
Which complex is definitely diamagnetic
A [FeF₆]³⁻
B [Fe(CN)₆]⁴⁻
C [CoF₆]³⁻
D [Ni(H₂O)₆]²⁺
Fe²⁺ is d⁶; CN⁻ is strong field → low spin d⁶ (t₂g⁶) → all paired → diamagnetic.
Which complex is more likely to be high spin
A [Fe(CN)₆]³⁻
B [FeF₆]³⁻
C [Co(NH₃)₆]³⁺
D [Ni(CO)₄]
F⁻ is weak field; Fe³⁺ (d⁵) with weak field gives high spin with 5 unpaired electrons.
Which is the correct order of field strength (weak → strong)
A CN⁻ < NH₃ < H₂O < I⁻
B I⁻ < H₂O < NH₃ < CN⁻
C NH₃ < H₂O < I⁻ < CN⁻
D H₂O < I⁻ < NH₃ < CN⁻
Spectrochemical series places I⁻ at weak end, CN⁻ at strong end.
The splitting energy in tetrahedral field is represented by
A Δo
B Δt
C Δp
D Δs
Δt denotes splitting for tetrahedral complexes.
Compared to octahedral splitting, tetrahedral splitting is
A larger and reversed
B smaller and reversed
C equal and same order
D equal but reversed
Δt is smaller (~4/9 of Δo) and the order of orbitals is reversed.
Which geometry is most common for coordination number 6
A Square planar
B Octahedral
C Tetrahedral
D Linear
Coordination number 6 typically gives octahedral geometry due to minimized repulsions.
The compound with highest melting point is usually
A Covalent molecular solid
B Ionic solid
C Metallic liquid
D Noble gas solid
Ionic solids have strong electrostatic forces, requiring high energy to melt.
The complex ion [Ag(NH₃)₂]⁺ has geometry
A Linear
B Bent
C Tetrahedral
D Octahedral
Coordination number 2 complexes are typically linear.
The coordination number of metal in [PtCl₆]²⁻ is
A 4
B 5
C 6
D 8
Six chloride ligands are attached to Pt → CN = 6.
Which complex is expected to show cis–trans isomerism
A [PtCl₆]²⁻
B [Co(NH₃)₆]³⁺
C [Pt(NH₃)₂Cl₂]
D [Ni(CO)₄]
Square planar MA₂B₂ complexes show cis/trans isomerism.
The ligand that can form a five-membered chelate ring most commonly is
A NH₃
B en
C Cl⁻
D I⁻
Ethylenediamine is bidentate and forms stable five-membered rings with metal ions.
Which statement is correct about chelate effect
A Chelates are always less stable
B Chelates are more stable than similar monodentate complexes
C Chelation decreases entropy
D Chelation prevents coordination completely
Chelate effect increases stability mainly due to favorable entropy change during complex formation.
Which type of isomerism occurs due to interchange of ligands between cationic and anionic complexes
A Linkage isomerism
B Coordination isomerism
C Geometrical isomerism
D Optical isomerism
Coordination isomerism occurs in salts containing both complex cation and complex anion.
In [Co(NH₃)₅Br]SO₄, the counter ion is
A NH₃
B Br⁻
C SO₄²⁻
D Co³⁺
Sulfate is outside the coordination sphere, balancing charge as counter ion.
The oxidation state of Co in [Co(NH₃)₅Br]SO₄ is
A +1
B +2
C +3
D +4
SO₄²⁻ is counter ion, so complex cation is +2. Inside: NH₃ neutral, Br⁻ = −1. Co −1 = +2 → Co = +3.
Which complex is most likely to be colored
A [Na(H₂O)₆]⁺
B [Mg(H₂O)₆]²⁺
C [Zn(NH₃)₄]²⁺
D [Cu(H₂O)₆]²⁺
Color in complexes commonly arises from d–d transitions; Cu²⁺ is d⁹ (transition metal ion) so it forms colored complexes.