Chemistry

Coordination Chemistry

325 Questions

Coordination chemistry focuses on coordination compounds, their structures, and their magnetic properties. The questions cover primary and secondary valencies, ligand types, and geometries of complexes. This topic is heavily tested in chemistry competitive exams and requires a good grasp of molecular structures.

primary and secondary valencycomplex geometriesligand field theorymagnetic properties of complexesisomerism in complexes

Coordination Chemistry Questions

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) uses of alkali and alkaline earth metals uses of s block elements group 1 elements: alkali metals

$Sr^{2+}$ forms a very unstable complex with $NO _{3-}$. A solution that was $0.001 M - Sr(ClO _{4}) _{2}$ and $0.05 M - KNO _{3}$ was found to have only $75$% of its strontium in the uncomplexed $Sr^{2+}$ form, the balance being $Sr(NO _{3})^{+}$. What is $K _{f}$ for complexation?

  1. $6.67$
  2. $0.15$
  3. $60$
  4. $26.67$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given 25% complexation (0.00025 M) and 75% free Sr2+ (0.00075 M), with [NO3-] = 0.05 M, Kf = [Sr(NO3)+] / ([Sr2+][NO3-]) = 0.00025 / (0.00075 * 0.05) = 0.00025 / 0.0000375 = 6.666...

Multiple choice pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

Nitrosy ligand binds to d-metal atoms in liner and bent fashion and behaves, respectively, as _______________.

  1. $NO^{+}$ and $NO^{+}$
  2. $NO^{+}$ and $NO^{-}$
  3. $NO^{-}$ and $NO^{-}$
  4. $NO^{-}$ and $NO^{+}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Linear nitrosyl (NO) ligands act as 3-electron donors (NO+), while bent nitrosyl ligands act as 1-electron donors (NO-).

Multiple choice chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

In solid state $PCl _{5}$ is a :

  1. covalent solid

  2. octahedral structure
  3. ionic solid with $[PCl _{6}]^{+}$ octahedral and $[PCl _{4}]^{-}$ tetrahedral
  4. ionic solid with $[PCl _{4}]^{+}$ tetrahedral and $[PCl _{6}]^{-}$ octahedral
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In solid state $PCl _5$ tries  to exist as oppositely charged ions like

(1) $PCl _4^{+}$ and (2) $PCl _6^{-}$ as the ionic bonding enhances the crystalline nature .

also $PCl _4^{+}$  is tetrahedral , while $PCl _6^{-}$ is octahedral . these structure fit well into each other which gives more stability to solid structure .

Hence option D is correct.

Multiple choice chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

In crystalline state $PCl _5$ exists as :

  1. $[PCl _4]^+Cl^-$
  2. $[PCl _4]^+[PCl _6]^-$
  3. $[PCl _3]^{2+}+2Cl^-$
  4. $[PCl _6]^+[PCl _4]^-$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In solid state, $PCl _5$ prefers to exist as oppositely charged ions like $[PCl _4]^+ [PCl _6]^-$ as ionic bonding enhances the crystalline nature. Also, $[PCl _4]^+$ is tetrahedral while $[PCl _6^-]$ is octahedral. These structures fit well into each other providing extra stability to the solid structure.


Hence, the correct option is (B).

Multiple choice chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

What is the hybridization state of cation part of solid $PCl _5$?

  1. $sp^3d^2$
  2. $sp^2$
  3. $sp^3$
  4. $sp^3d$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In solid state, $PCl _5$ prefers to exist as oppositely charged ions like $[PCl _4]^+ PCl _6^-$ as ionic bonding enhances the crystalline nature. Also, $[PCl _4]^+  = sp^3$ is tetrahedral while $[PCl _6^-]$ is octahedral. These structures fit well into each other providing extra stability to the soild structure.

Thus, solid $PCl _5$ exist as $[PCl _4]^+[PCl _6]^-$
The cationic part of $PCl _5$ is$[PCl _4]^+$.
In $PCl _4^+$, Phosphorous forms $4\ \sigma-bonds$. 
Hence, the hybridization is $sp^3$.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

$Cr - C$ bond in the compound $[Cr(CO) _6]$ shows $\pi$ - character due to :

  1. covalent bonding

  2. coordinate bonding

  3. synergic bonding

  4. ionic bonding
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  1. Synergic bonding is the description of the bonding of $\pi$ - configuration ligands to the transition metal which involves donation of electrons through back bonding.
    2. Mainly carbonyl ligands in complex compounds involves in this type of bonding.
Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Consider the following complexes $[V(CO) _6]^-,[Cr(CO) _6]$ and $[Mn(CO) _6]^+$. Then incorrect statement(s) about metal carbonyls is /are

  1. 'C-O' bond is strongest in the cation and weakest in the anion

  2. 'C-O' bond order is less in the cation than in anion

  3. 'C-O' bond longer in the cation than in anion or neutral carbonyl

  4. 'M-C' bond order is higher in the carbon than in anionic or neutral carbonyl.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In metal carbonyls, as the negative charge on the complex increases, back-bonding from metal to CO increases, strengthening the M-C bond and weakening the C-O bond. Thus, the C-O bond is weakest in the anion and strongest in the cation.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

If CO ligands are substituted by NO in respective neutral carbonyl compounds then which of the following will not be correct formula?

  1. $Cr(CO) _3(NO) _2$
  2. $Fe(CO) _2(NO) _2$
  3. $Cr(NO) _4$
  4. $Ni(CO) _2(NO) _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Using the 18-electron rule, Cr(CO)6 has 18 electrons. Substituting CO (2e) with NO (3e) changes the count. Cr(CO)3(NO)2 would have 6 + 6 + 6 = 18 electrons. However, Cr(NO)4 is not a stable neutral carbonyl-like complex following this substitution pattern.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Which of the following statement is correct regarding metal carbonyl?

  1. In ${Mn} _{2}{(CO)} _{10}$ bond order of $Mn-Mn$ is $0$
  2. In ${Fe} _{2}{(CO)} _{9}$ bond order of $Fe-Fe$ is $1$
  3. In $Ni{(CO)} _{4}$, all bond length are same
  4. $Fe{(CO)} _{5}$ is diamagnetic
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Fe(CO)5 is a 18-electron complex with a trigonal bipyramidal structure. All electrons are paired in the d-orbitals, making it diamagnetic.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Which of the following organometallic compound

is $\sigma $ and $\pi $ bonded?

  1. $[Fe(\eta ^{5}-C _{5}H _{5}) _{2}]$
  2. $[PtCl _{3}(\eta ^{2}-C _{2}H _{4})]$
  3. $[Co(CO) _{5}NH _{3}]^{2+}$
  4. $Al(CH _{3}) _{3}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$[PtCl _{3}(\eta ^{2}-C _{2}H _{4})]$ and $[Fe(\eta ^{5}-C _{5}H _{5}) _{2}]$ are pi bonded organometallic compound.

$Al(CH _3) _3$ 
is sigma bonded organometallic compound.
$[Co(CO) _{5}NH _{3}]^{2+}$ is sigma and pi bonded organometallic compound.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Which of the following organometallic compound is $\sigma$ and $\pi$ bonded -

  1. $[Fe(\eta^{5} - C _5H _5) _2]$
  2. $K[PtCl _3(\eta^{2} - C _2H _40]$
  3. $[Co(CO) _5NH _3]^{+2}$
  4. $Fe(CH _3) _3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Option (C) is correct.
$[Co(CO) _5NH _3]^{+2}$ is $\sigma$ and $\pi$ bonded.
In this organometallic compound,bond between cobalt and $CO$ ligands have both $\sigma$ and $\pi$ character.$\sigma$- bond formation between metal and carbon of $CO$ takes place by overlap of filled bonding $\pi _{2p}$ of $CO$ with an empty metal $d$- orbital.
The 2nd overlap takes place between metal $d$- orbital with an empty antibonding pi orbital of the $CO$ resulting in additional $\pi$- bond between the metal and same $CO$ molecule.