Basic Terms Questions in English

(D) The compound $[Cu(NH_3)_4]SO_4$ can be dissociated as $[Cu(NH_3)_4]^{2+}$ and $SO_4^{2-}$.
$1$. The bond between the complex cation $[Cu(NH_3)_4]^{2+}$ and the anion $SO_4^{2-}$ is electrovalent (ionic).
$2$. Within the complex ion $[Cu(NH_3)_4]^{2+}$,the $NH_3$ ligands form coordinate bonds with the $Cu^{2+}$ central metal ion.
$3$. Within the $NH_3$ molecule itself,there are covalent bonds between $N$ and $H$ atoms.
$4$. Within the $SO_4^{2-}$ ion,there are covalent bonds between $S$ and $O$ atoms.
Therefore,the compound contains electrovalent,covalent,and coordinate bonds.

(B) double salt is an addition compound formed by the combination of two stable salts in stoichiometric proportions,which loses its identity in aqueous solution.
$B$. $FeSO_4 \cdot (NH_4)_2SO_4 \cdot 6H_2O$ (Mohr's salt) is a classic example of a double salt.

(B) The chemical formula of Mohr's salt is $FeSO_4 \cdot (NH_4)_2SO_4 \cdot 6H_2O$.
It is a double salt containing $6$ water molecules of crystallization.

(C) The compound $(NH_4)_2SO_4 \cdot Fe_2(SO_4)_3 \cdot 24H_2O$ is known as ferric ammonium alum.
In this compound,iron exists in the $+3$ oxidation state $(Fe^{3+})$.
Ferric salts,specifically those containing $Fe^{3+}$ ions,typically exhibit a pale violet or light purple colour in their crystalline form.

(B) Potassium ferricyanide is a coordination compound with the $IUPAC$ name potassium hexacyanidoferrate$(III)$.
In this complex,the iron atom is in the $+3$ oxidation state $(Fe^{3+})$.
The cyanide ligand $(CN^-)$ has a charge of $-1$.
To balance the charge of the complex $[Fe(CN)_6]^{x}$,we have $x + 6(-1) = -3$,so $x = -3$.
Therefore,the complex ion is $[Fe(CN)_6]^{3-}$.
To neutralize this,three potassium ions $(K^+)$ are required.
Thus,the formula is $K_3[Fe(CN)_6]$.

(C) Mohr's salt,also known as ferrous ammonium sulphate,is a double salt with the chemical formula $(NH_4)_2SO_4 \cdot FeSO_4 \cdot 6H_2O$.
It is classified as a double salt because it contains two different cations,$Fe^{2+}$ and $NH_4^{+}$,which dissociate completely in an aqueous solution.

(D) . Potash alum is a double salt with the formula $K_2SO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O$.
Double salts dissociate completely into their constituent ions in aqueous solution,whereas coordination compounds like $K_4[Fe(CN)_6]$ do not.

(B) The correct answer is $B$.
Turnbull's blue is chemically known as ferrous ferricyanide,with the formula $Fe_3[Fe(CN)_6]_2$.

(B) In the coordination compound $K_4[Fe(CN)_6]$,the central metal ion $Fe^{2+}$ is surrounded by six $CN^-$ ligands.
These ligands are directly attached to the central metal ion through coordinate covalent bonds,which corresponds to the secondary valency.
The $K^+$ ions are outside the coordination sphere and satisfy the primary valency (oxidation state) of the metal ion.
Therefore,$(CN)^-$ ions are linked with secondary valency.

(C) The chemical formula for cuprammonium sulphate is $[Cu(NH_3)_4]SO_4$.
In this complex ion,the central metal atom is $Cu^{2+}$.
The ligand is ammonia $(NH_3)$,which is a monodentate ligand.
Since there are $4$ ammonia molecules attached to the central metal ion,the coordination number is $4$.

(B) The correct answer is $(b)$.
An oxalate ion,$C_2O_4^{2-}$,acts as a bidentate ligand because it uses two oxygen atoms to form two coordinate covalent bonds with the central metal ion.

(B) The coordination number is determined by the number of donor atoms directly bonded to the central metal ion.
In the complex $[Co(en)_2Br_2]Cl_2$,the ligand $en$ (ethylenediamine) is a bidentate ligand,meaning it donates $2$ donor atoms per ligand.
The ligand $Br^-$ is a monodentate ligand,meaning it donates $1$ donor atom per ligand.
Coordination Number $= (2 \times \text{number of } en) + (1 \times \text{number of } Br^-) = (2 \times 2) + (1 \times 2) = 4 + 2 = 6$.

(D) In chelation,ring formation occurs because two or more donor atoms from the same ligand coordinate with the central metal atom.
This process requires the ligand to be polydentate.
$Acetate$,$cyanide$,and $ammonia$ are monodentate ligands,meaning they have only one donor atom and cannot form a ring.
$Oxalate$ $(C_2O_4^{2-})$ is a bidentate ligand that coordinates through two oxygen atoms,forming a stable five-membered ring with the metal ion.
Therefore,$oxalate$ forms a chelate.

(A) According to Werner's theory:
$1$. The primary valency corresponds to the oxidation state of the metal and is ionizable. It is satisfied by negative ions.
$2$. The secondary valency corresponds to the coordination number of the metal and is non-ionizable. It is satisfied by ligands (neutral molecules or negative ions).
Therefore,the correct statement is that primary valency can be ionized.

(B) bidentate ligand is a ligand that has two donor atoms that coordinate directly to the central metal atom in a complex.
Ethylenediamine $(NH_2CH_2CH_2NH_2)$ is a classic example of a bidentate ligand because it has two nitrogen atoms that can donate lone pairs to the metal ion.
$CN^{-}$ and $SCN^{-}$ are monodentate ligands.
$EDTA^{4-}$ is a hexadentate ligand.

(D) The coordination number is defined as the total number of sigma bonds formed by the central metal atom with the ligands.
In the complex ion $[Pt(NH_3)_4Cl_2]^{2+}$,the central metal $Pt$ is bonded to four $NH_3$ molecules and two $Cl^{-}$ ions.
Since both $NH_3$ and $Cl^{-}$ are monodentate ligands,each contributes one coordinate bond.
Therefore,the coordination number = $4 \times (1) + 2 \times (1) = 6$.

(D) hexadentate ligand is a ligand that can form six coordinate bonds with a central metal atom or ion.
$EDTA^{4-}$ (Ethylenediaminetetraacetate ion) has six donor atoms: two nitrogen atoms and four oxygen atoms from the carboxylate groups.
Therefore,it acts as a hexadentate ligand.
$2, 2'-$dipyridyl is a bidentate ligand.
Dimethylglyoxime is a bidentate ligand.
Aminodiacetate ion is a tridentate ligand.
Thus,the correct option is $(d)$.

(C) According to Werner's theory and modern coordination chemistry,the primary valency corresponds to the oxidation state of the central metal atom,while the secondary valency corresponds to the coordination number of the central metal atom.
Therefore,the coordination number is equal to the secondary valency.

(D) ligand is defined as an ion or a molecule that is bound to a central metal atom or ion in a coordination entity.
These species donate a pair of electrons to the central metal atom or ion to form a coordinate covalent bond.
Therefore,ligands can be either ions (anions or cations) or neutral molecules.

(B) The coordination number of a metal complex is defined as the total number of sigma bonds formed by ligands with the central metal atom or ion.
In the complex $[Cr(H_2O)_6]^{3+}$,there are $6$ water molecules acting as monodentate ligands.
Therefore,the coordination number is $6 \times 1 = 6$.
In the other options,$[Zn(CN)_4]^{2-}$,$[Cu(CN)_4]^{2-}$,and $[Ni(NH_3)_4]^{2+}$ all have $4$ ligands,resulting in a coordination number of $4$.

(B) The chemical formula for cuprammonium sulphate is $[Cu(NH_3)_4]SO_4$.
When it dissolves in water,it undergoes dissociation as follows:
$[Cu(NH_3)_4]SO_4 \rightleftharpoons [Cu(NH_3)_4]^{2+} + SO_4^{2-}$.
Thus,it produces $2$ ions in total ($1$ complex cation and $1$ sulphate anion).

(A) The coordination number is defined as the total number of sigma bonds formed by the central metal atom or ion with the ligands.
In the complex $[Cu(H_2O)_4]^{2+}$,the central metal ion is $Cu^{2+}$.
There are $4$ water molecules $(H_2O)$ acting as monodentate ligands attached to the central metal ion.
Therefore,the coordination number $= 4 \times 1 = 4$.

(C) The primary valence of a metal ion in a coordination compound corresponds to its oxidation state.
For the complex $K_2[Ni(CN)_4]$,let the oxidation state of $Ni$ be $x$.
The oxidation state of $K$ is $+1$ and $CN$ is $-1$.
Setting the sum of oxidation states equal to zero: $2(+1) + x + 4(-1) = 0$.
$2 + x - 4 = 0$.
$x - 2 = 0$.
$x = +2$.
Thus,the primary valence of $Ni$ is $2$.

(B) The correct answer is $B$.
$Ag^{+}$ ion reacts with an excess of $CN^{-}$ ions to form the dicyanoargentate$(I)$ complex,which is $[Ag(CN)_2]^{-}$.
In this complex,the coordination number of the central metal ion $Ag^{+}$ is $2$.

(B) According to Lewis theory,ligands act as electron pair donors. Since species that donate electron pairs are defined as Lewis bases,ligands are basic in nature.

(C) The coordination number of a central metal atom or ion in a complex is defined as the total number of ligand donor atoms that are directly bonded to the central metal atom or ion through coordinate covalent bonds (which are essentially $\sigma$-bonds).
Therefore,the coordination number of a metal = number of $\sigma$-bonds formed by the metal with the ligands.

(D) In $K_4[Fe(CN)_6]$,the species retains its identity in solid as well as in solution state. It dissociates to give $[Fe(CN)_6]^{4-}$ ions,which do not further dissociate into $Fe^{2+}$ and $CN^-$ ions. Hence,it is a complex salt.

(A) Monodentate ligands are $Lewis$ bases that donate a single pair of electrons to a metal atom through one donor atom.
Therefore,they possess only one co-ordinate site.

(D) $EDTA^{4-}$ (Ethylenediaminetetraacetate ion) is a hexadentate ligand.
It contains two nitrogen atoms and four oxygen atoms as donor sites.
Therefore,it forms $6$ coordinate bonds with a central metal atom or ion,making its denticity $6$.

(B) $ligand$ is an ion or molecule that binds to a central metal atom or ion to form a coordination complex. $Ligands$ act as Lewis bases by donating a pair of electrons to the metal ion.

(B) The complexes can be written in the form of coordination entities as follows:
$(a)$ $[Co(NH_3)_6]Cl_3$
$(b)$ $[Co(NH_3)_5Cl]Cl_2$
$(c)$ $[Co(NH_3)_4Cl_2]Cl$
Primary valency corresponds to the oxidation state of the central metal atom,which is balanced by the ionizable chloride ions outside the coordination sphere.
In $(a)$,there are $3$ $Cl^-$ ions,so primary valency is $3$.
In $(b)$,there are $2$ $Cl^-$ ions,so primary valency is $2$.
In $(c)$,there is $1$ $Cl^-$ ion,so primary valency is $1$.
Thus,the primary valencies are $3, 2, 1$.

(C) ligand is defined as an atom,molecule,or ion that can donate at least one lone pair of electrons to the central metal atom or ion to form a coordinate covalent bond.
Therefore,ligands can be neutral molecules (e.g.,$H_2O$,$NH_3$) or negatively charged ions (e.g.,$Cl^-$,$CN^-$).

(B) The chemical formula of potassium ferricyanide is $K_3[Fe(CN)_6]$.
In this coordination compound,the central metal ion is $Fe^{3+}$ and the species attached to the central metal ion by coordinate bonds are the ligands.
Here,the $CN^{-}$ ions act as ligands because they donate a lone pair of electrons to the central metal ion.

(B) The coordination number of $Al^{3+}$ in its common coordination complexes,such as $[Al(H_2O)_6]^{3+}$ or $[AlF_6]^{3-}$,is $6$.

(B)
Ligands that have two donor atoms to coordinate with the central metal ion are called bidentate ligands.
$C_2O_4^{2-}$ (oxalate ion) has two oxygen donor atoms and is a bidentate ligand.

(B) The chemical formula for lithium tetrahydroaluminate is $Li[AlH_4]$.
In this complex,the central metal atom is $Al$ and the species attached to it are the ligands.
The complex ion is $[AlH_4]^-$,where four hydride ions $(H^-)$ act as ligands attached to the aluminum atom.
Therefore,the ligand is $H^-$.

(B) Potassium ferrocyanide,potassium ferricyanide,and tetrammine copper $(II)$ sulphate are coordination compounds.
Ferrous ammonium sulphate,$(NH_4)_2SO_4 \cdot FeSO_4 \cdot 6H_2O$,is a double salt.
Double salts dissociate completely into their constituent ions in aqueous solution,whereas coordination compounds retain their complex ion structure in solution.
Therefore,ferrous ammonium sulphate is the odd one out.

(D) In coordination chemistry,a ligand is an ion or molecule that acts as a Lewis base by donating a pair of electrons to a central metal atom to form a coordination complex.
$NH_3$ has a lone pair on the nitrogen atom.
$CN^{-}$ has a lone pair on the carbon atom.
$F^{-}$ has lone pairs on the fluorine atom.
Since all these species can donate an electron pair to a metal center,they all act as Lewis bases (ligands).

(B) In coordination chemistry,negative ligands are named with the suffix $-o$.
For example,the sulfate ion $SO_4^{2-}$ is named as $sulphato$ when acting as a ligand.
Therefore,$sulphato$ is a negative ligand.

(B) ligand is defined as an atom,ion,or molecule that donates a pair of electrons to the central metal atom or ion to form a coordinate covalent bond. Therefore,ligands act as Lewis bases by donating an $e^{-}$ pair.

(D) Ligands are species that donate a pair of electrons to the central metal atom or ion to form a coordinate bond.
Common donor atoms in ligands include electronegative atoms with lone pairs of electrons,such as $N$,$O$,$P$,$S$,and $X$ (halogens).
Since both nitrogen $(N)$ and oxygen $(O)$ are common donor atoms found in many ligands (e.g.,$NH_3$,$H_2O$,$OH^-$),the correct option is $(d)$.

(B) The coordination number of a metal ion in a complex is the number of ligand donor atoms to which the metal is directly bonded.
While coordination numbers of $4$ and $6$ are the most common in coordination chemistry,higher coordination numbers are possible depending on the size of the metal ion and the steric requirements of the ligands.
For example,in complexes like $[Ce(NO_3)_6]^{2-}$,the coordination number is $12$.
Thus,the highest possible coordination number observed in stable coordination complexes is $12$.

(C) The number of neutral molecules or negative groups (ligands) directly bonded to the central metal atom or ion through coordinate bonds is defined as the $Coordination \ number$ of the metal ion.

(B) $EDTA$ (Ethylenediaminetetraacetic acid) is a hexadentate ligand that binds to metal cations through its six donor atoms (two nitrogen and four oxygen atoms).
This process of binding to a single metal ion through multiple donor atoms results in the formation of a stable ring-like structure known as a chelate.
Therefore,$EDTA$ forms chelates with metal cations.

(A) In coordination compounds,the ligand acts as a Lewis base by donating a lone pair of electrons to the central metal atom or ion,which acts as a Lewis acid. This donation of an electron pair results in the formation of a coordinate covalent bond,also known as a dative bond.

(D) The coordination number is defined as the total number of ligand donor atoms that are directly bonded to the central metal atom or ion through coordinate bonds.
In the complex $[Co(NH_3)_3Cl_3]$,the central metal atom $Co$ is bonded to $3$ ammonia $(NH_3)$ molecules and $3$ chloride $(Cl^-)$ ions.
Since both $NH_3$ and $Cl^-$ are monodentate ligands,each contributes $1$ to the coordination number.
Therefore,the total coordination number is $3 + 3 = 6$.

(A) The general formula for alum is $M_2SO_4 \cdot R_2(SO_4)_3 \cdot 24H_2O$.
Here,$M$ represents a monovalent cation (e.g.,$K^{+}$,$Na^{+}$) and $R$ represents a trivalent cation (e.g.,$Al^{3+}$,$Fe^{3+}$).
Therefore,$K_2SO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O$ is the correct formula for potash alum.

(D) $K_4[Fe(CN)_6]$ is a coordination compound.
Upon dissociation in an aqueous solution,it ionizes as follows:
$K_4[Fe(CN)_6] \rightarrow 4K^{+} + [Fe(CN)_6]^{4-}$
Total number of ions = $4$ (potassium ions) + $1$ (complex ion) = $5$ ions.

(B) The coordination compound $[Co(H_2O)_6]Cl_2$ dissociates in aqueous solution as follows:
$[Co(H_2O)_6]Cl_2 (aq) \rightarrow [Co(H_2O)_6]^{2+} (aq) + 2Cl^{-} (aq)$
From the dissociation,we get one complex cation $[Co(H_2O)_6]^{2+}$ and two chloride anions $2Cl^{-}$.
Total number of ions produced = $1 + 2 = 3$.

(B) The chemical formula of sodium nitroprusside is $Na_2[Fe(CN)_5NO]$.
It is a coordination compound where the central metal ion is $Fe^{2+}$ and the ligands are five $CN^-$ ions and one $NO^+$ (nitrosonium) ion.
The correct option is $B$.