Chemistry

Coordination Chemistry

319 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 coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

Which of the following complexes will have a tetrahedral shape?

  1. $[PdCl _4]^{2-}$
  2. $[Pd(CN) _4]^{2-}$
  3. $[Ni(CN) _4]^{2-}$
  4. $[NiCl _4]^{2-}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$[NiCl _4]^{2-}=$ $Cl^-\rightarrow $ Weak field ligand.

$\Rightarrow Ni^{2+}\Rightarrow [Ar]3d^8$
As the ligands is weak field ligands the complex has tetrahedral geometry of $sp^3$ hybridisation.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

The two isomers X and Y with the formula $Cr(H _2O) _5ClBr _2$ were taken for experiment on depression in freezing point. It was found that one mole of X gave depression corresponding to $2$ moles of particles and one mole of Y gave depression due to $3$ moles of particles. The structural formulae of X and Y respectively are:

  1. $[Cr(H _2O) _5Cl]Br _2$; $[Cr(H _2O) _4Br _2]Cl\cdot H _2O$
  2. $[Cr(H _2O) _5Cl)]Br _2$; $[Cr(H _2O) _3ClBr]\cdot 2H _2O$
  3. $[Cr(H _2O) _5Br]BrCl$; $[Cr(H _2O) _4ClBr]Br\cdot H _2O$
  4. $[Cr(H _2O) _4Br _2]Cl\cdot H _2O$; $[Cr(H _2O) _5Cl]Br _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Cr(H _2O) _5ClBr _2\longrightarrow$ 2 moles of particle.

It compoubnd is $[Cr(H _2O) _4(Br _2)]Cl.H _2O$
It gives $[Cr(H _2O) _4Br _2]^{+},C\bar l\Rightarrow $ Two particles.
So, $X=[Cr(H _2O) _4Br _2]Cl.H _2O$
If $Y=[Cr(H _2O) _5Cl]Br _2$
It gives $[Cr(H _2O) _5Cl^{2+},2B\bar r\Rightarrow $ 3 particles.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

Number of chlorides satisfying secondary valency in $CoCl _{3},\ 4NH _{3}$

  1. $1$
  2. $2$
  3. $3$
  4. $6$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In CoCl3 * 4NH3, the coordination compound is [Co(NH3)4Cl2]Cl. The secondary valency (coordination number) is 6, satisfied by 4 NH3 and 2 Cl ions. The remaining Cl ion is outside the coordination sphere.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

The co-ordination number of a metal in co-ordination compound is:

  1. same as primary valency

  2. sum of primary and secondary valences

  3. same as secondary valency

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The secondary valency is equal to the coordination number the secondary valency are non ionizable valencies. These are satisfied by neutral molecules or negative ions.  For example in $[Ni(CO) _4]$ the coordination number of Ni metal is four and its secondary valency is also four.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

According to Werner's theory the primary valency and secondary valency in complex $[Co(NH _3) _4Cl _2]Cl$ is respectively:

  1. 3,3

  2. 3, 6

  3. 6, 3

  4. 4, 2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The primary valency is the oxidation state of the metal ion and the coordination number of the metal is the secondary valency of the metal ion. 


The oxidation number of $Co = x + 0 -3 = 0$

                                           $x = 3$

The primary valency is 3 and the secondary valency is 6. Therefore, the correct option is B.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

Which of the following is not correctly matched ? 

  1. $[Fe (CN) _6]^{3-} d^2 sp^3$, paramagnetic
  2. $[Ni (CO) _4] -sp^3$, diamagnetic
  3. $[Fe(en) _3]^{+3} - sp^3 d^2$, paramagnetic
  4. $[FeCl _2 (H _2O) _2] sp^3$, paramagnetic
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Option C is correctly matched because Fe(III) in [Fe(en)3]3+ has a d5 configuration with a strong field ligand (en), forcing inner orbital coordination resulting in sp3d2 hybridization and paramagnetism due to one unpaired electron. The other options contain incorrect hybridizations or magnetic properties for their respective coordination complexes.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

According to Werner's theory state which of the following statements are correct:


1. Ligands are connected to the metal ions by covalent bonds
2. Secondary valencies have directional properties
3. Secondary valencies are non-ionisable.

  1. 1, 2, and 3 are correct

  2. 2 and 3 are correct

  3. 1 and 2 are correct

  4. 1 ,2 are correct,and 3 is not correct
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Werner's theory, ligands are attached to the central metal ion by coordinate covalent bonds (secondary valency), these valencies have specific spatial arrangements (directional), and they are non-ionizable.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

Several octahedral complexes are possible from combinations of $Co^{3+}, Cl^{-}$ and $NH {3}$. The correct statement(s) regarding the octahedral coordination entities having the formula .$[Co(NH _{3}) _{n}Cl _{6 - n}]^{(n - 3)+}$ with $n\geq 3$, is/ are____________.

  1. At most six octahedral complexes are possible

  2. One of the complexes is homoleptic

  3. All the complexes are paramagnetic
  4. Some of the complexes dissociate in water to give $Co^{3+}$ and $Cl^{-}$ ions
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

$[Co(NH _3) _nCl _{6-n}]^{(n-3)^+}$  $n\ge 3$

For $n=3,n=4,n=5,n=6$
For $n=6\Rightarrow [Co(NH _3) _6]^{3+}=$ is  homopletic due to all 6 same ligands.
For $n=5\Rightarrow [Co(NH _3) _6]^{2+}$
For $n=4\Rightarrow [Co(NH _3) _6]^+=$
For $n=3\Rightarrow [Co(NH _3) _6]$
Only $4$ octahedral complex are possible.
One of them is homoleptic.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

In the separation of $Cu^{2+}$ and $Cd^{2+}$ in the second group of qualitative analysis of cations, tetraamine copper (ll) sulphate and tetraamine cadmium (ll) sulphate react with KCN to form corresponding cyano complexes. Which of the following pairs of complexes and their relative stability enables the separation of $Cu^{2+}$ and $Cd^{2+}$?

  1. $K _2[Cu(CN) _4]$ is less stable and $K _2[Cd(CN) _4]$ is more stable
  2. $K _3[Cu(CN) _4]$ is more stable and $K _2[Cd(CN) _4]$ is less stable
  3. $K _3[Cu(CN) _4]$ is less stable and $K _2[Cd(CN) _4]$ is more stable
  4. $K _2[Cu(CN) _4]$ is more stable and $K _2[Cd(CN) _4]$ is less stable
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The separation of Cu2+ and Cd2+ relies on the relative stability of their cyano complexes. The copper complex [Cu(CN)4]3- is more stable than the cadmium complex [Cd(CN)4]2-, allowing for selective precipitation or reaction.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

Primary and secondary valency of platinum in the complex $[Pt(en) _{2}Cl _{2}]$ are:

  1. $4,6$
  2. $2,6$
  3. $4,4$
  4. $2,4$
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

The Given complex $[Pt(en) _2Cl _2]$ The primary valence is its oxidation number i.e +2 and the secendory valency is its coordination number i.e 6 in this case.(The en ligand is bidentate, and Cl is monodentate).The second possibility  is that compound can exist as $[Pt(en) _2]Cl _2$ and hence the primary valency can also be +2 and  secondary valence is 4. Hence option B and D are correct

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

The number of complexes that can be can be made with varying $NH _3$ ligands to satisfy primary and secondary valencies of platinum are:

Complex; [$PtCl _4\cdot xNH _3$]   

  1. 5

  2. 3

  3. 4

  4. 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The correct answer is 5.
The number of complexes that can be can be made with $PtCl _4\cdot xNH _3$ are :
 
I. $[Pt(NH _3) _6]Cl _4$

II. $[Pt(NH _3) _5Cl]Cl _3$

III. $[Pt(NH _3) _4Cl _2]Cl _2$

IV: $ [Pt(NH _3) _3Cl _3]Cl$

V: $[Pt(NH _3) _2Cl _4]$

Option A is correct.