Basic Terms Questions in English

(B) tetradentate ligand is a ligand that can form $4$ coordinate bonds with a central metal atom or ion.
$1$. Ethylene diamine tetracetato $(EDTA^{4-})$ is a hexadentate ligand.
$2$. Triethylene tetramine $(trien)$ has $4$ nitrogen donor atoms,making it a tetradentate ligand.
$3$. Dimethyl glyoximato $(dmg^-)$ is a bidentate ligand.
$4$. Oxalato $(C_2O_4^{2-})$ is a bidentate ligand.
Therefore,the correct option is $B$.

(D) Dimethyl glyoximato (dmg) is a bidentate ligand with the structure $(CH_3C=NOH)_2$.
In the structure of dimethyl glyoxime,there are two $=N-OH$ groups attached to the carbon atoms.
Therefore,the number of $=N-OH$ groups present in dimethyl glyoximato is $2$.

(C) $EDTA$ stands for Ethylenediaminetetraacetate ion.
It contains two nitrogen atoms and four oxygen atoms as donor sites.
Therefore,it acts as a hexadentate ligand,meaning it has $6$ donor groups.

(A) An ambidentate ligand is a ligand that can coordinate to a central metal atom through two different donor atoms.
$NO_{2}^{-}$ is an ambidentate ligand because it can coordinate through either the nitrogen atom $(N)$ or the oxygen atom $(O)$.
$H_{2}O$ and $NH_{3}$ are monodentate ligands.
$C_{2}O_{4}^{2-}$ (oxalate ion) is a bidentate ligand.

(D) In the coordination compound $[CoCl_{2}(NH_{3})_{4}]Cl$,the central metal ion is $Co^{3+}$.
The ligands present inside the coordination sphere are $4$ $NH_{3}$ molecules and $2$ $Cl^{-}$ ions.
Therefore,the total number of ligands (coordination number) is $4 + 2 = 6$.

(B) monodentate ligand is a ligand that binds to a central metal atom through only one donor atom.
Water $(H_2O)$ is a monodentate ligand because it uses only the oxygen atom to donate a lone pair.
Oxalato $(C_2O_4^{2-})$,ethylenediamine $(en)$,and dimethylglyoximato $(dmg^-)$ are all bidentate ligands.

(D) The chemical formula of diethylene triamine (dien) is $NH_2-CH_2-CH_2-NH-CH_2-CH_2-NH_2$.
It contains $3$ nitrogen atoms,each having a lone pair of electrons that can be donated to a central metal ion.
Therefore,it acts as a tridentate ligand with $3$ donor groups.

(C) neutral complex is a coordination compound that carries no net electrical charge.
In the given options:
$(A)\ [Fe(H_2O)_6]Cl_3$ dissociates into $[Fe(H_2O)_6]^{3+}$ and $3Cl^-$,making it a cationic complex.
$(B)\ [Ni(NH_3)_6]Cl_2$ dissociates into $[Ni(NH_3)_6]^{2+}$ and $2Cl^-$,making it a cationic complex.
$(C)\ [Pt(NH_3)_2Cl_2]$ has no ionizable groups outside the coordination sphere and carries a net charge of $0$,making it a neutral complex.
$(D)\ K[Ag(CN)_2]$ dissociates into $K^+$ and $[Ag(CN)_2]^-$,making it an anionic complex.

(C) Barium chloride $(BaCl_2)$ reacts with sulfate ions $(SO_4^{2-})$ to form a white precipitate of barium sulfate $(BaSO_4)$.
For a complex to give this precipitate,the $SO_4^{2-}$ ion must be present as a counter-ion outside the coordination sphere.
In the complex $[Co(NH_3)_5NO_2]SO_4$,the sulfate ion is present as a counter-ion.
The reaction is: $SO_4^{2-} (aq) + Ba^{2+} (aq) \rightarrow BaSO_4 (s) \text{ (White precipitate)}$.

(B) The dimethylglyoximato ligand,denoted as $dmg^-$,is a bidentate ligand.
It coordinates to the central metal ion through two nitrogen atoms.
Therefore,the number of donor atoms in a single dimethylglyoximato ligand is $2$.

(B) The complex $K_3[Fe(CN)_6]$ dissociates as $3K^+ + [Fe(CN)_6]^{3-}$.
Let the oxidation state of $Fe$ be $x$.
In the complex ion $[Fe(CN)_6]^{3-}$,the charge on $CN^-$ is $-1$.
So,$x + 6(-1) = -3$.
$x - 6 = -3 \Rightarrow x = +3$.
The coordination number is the number of ligand donor atoms bonded to the central metal ion. Since $6$ $CN^-$ ligands are attached,the coordination number is $6$.

(A) neutral complex is a coordination compound that carries no net electrical charge.
In the complex $[Pt(NH_3)_2Cl_2]$,the oxidation state of $Pt$ is $+2$,$NH_3$ is neutral $(0)$,and $Cl$ is $-1$. The total charge is $+2 + 2(0) + 2(-1) = 0$.
Therefore,$[Pt(NH_3)_2Cl_2]$ is a neutral complex.

(A) complex salt containing both complex cations and complex anions is known as a coordination isomer or a salt where both parts are coordination entities.
In the compound $[Pt(NH_3)_4][PtCl_6]$,the cation is $[Pt(NH_3)_4]^{2+}$ and the anion is $[PtCl_6]^{2-}$.
Therefore,this compound contains both complex cations and complex anions.

(A) complex anion is a negatively charged coordination entity.
In $Na_3[Co(NO_2)_6]$,the coordination entity is $[Co(NO_2)_6]^{3-}$,which is a complex anion.
In $Na_3[Co(NO_2)_6]$ (Sodium hexanitrocobaltate$(III)$),the complex part is the anion.
In $K_4[Fe(CN)_6]$,the complex part is also an anion.
Option $A$ represents a compound with a complex anion.

(C) neutral complex is one that carries no net charge.
$1$. $[Ni(CN)_4]^{2-}$ is an anionic complex with a charge of $-2$.
$2$. $Na_3[AlF_6]$ is an ionic compound consisting of $Na^+$ ions and $[AlF_6]^{3-}$ complex ions.
$3$. $[Co(NH_3)_3(NO_2)_3]$ has no net charge because the oxidation state of $Co$ is $+3$,and it is balanced by three neutral $NH_3$ ligands $(0 \times 3 = 0)$ and three anionic $NO_2^-$ ligands $(-1 \times 3 = -3)$. Thus,$+3 + 0 - 3 = 0$.
$4$. $[Cu(NH_3)_4]^{2+}$ is a cationic complex with a charge of $+2$.
Therefore,the neutral complex is $[Co(NH_3)_3(NO_2)_3]$.

(C) An anionic ligand is a negatively charged ligand.
In the complex $[Ni(CN)_4]^{2-}$,the ligand is cyanide $(CN^-)$,which is an anionic ligand.
In the other options:
- Tetraamminecopper$(II)$ ion: $[Cu(NH_3)_4]^{2+}$ contains neutral $NH_3$ ligands.
- Pentaammineaquacobalt$(III)$ iodide: $[Co(NH_3)_5(H_2O)]I_3$ contains neutral $NH_3$ and $H_2O$ ligands.
- Pentacarbonyliron$(0)$: $[Fe(CO)_5]$ contains neutral $CO$ ligands.
Therefore,the correct option is $C$.

(B) Let us analyze the charge on the complex ion for each option:
$A$: $[Co(en)_{3}]Cl_{3} \rightarrow [Co(en)_{3}]^{3+} + 3Cl^{-}$. The complex ion has a $+3$ charge.
$B$: $K_{3}[Al(C_{2}O_{4})_{3}] \rightarrow 3K^{+} + [Al(C_{2}O_{4})_{3}]^{3-}$. The complex ion has a $-3$ charge.
$C$: $[Ni(CO)_{4}]$ is a neutral complex with $0$ charge.
$D$: $[Ag(NH_{3})_{2}]Cl \rightarrow [Ag(NH_{3})_{2}]^{+} + Cl^{-}$. The complex ion has a $+1$ charge.
Therefore,the compound with a net negative charge on the complex ion is Potassium trioxalatoaluminate$(III)$.

(C) The primary valence of a central metal atom in a coordination compound corresponds to its oxidation state.
In $CoCl_{3}$,the oxidation state of $Co$ is calculated as follows:
$x + 3(-1) = 0$
$x - 3 = 0$
$x = +3$
Therefore,the primary valence of $Co$ is $3$.

(A) According to Werner's coordination theory,the primary valence corresponds to the oxidation state of the central metal atom.
It is ionisable and is satisfied by negative ions.
Therefore,it is also known as the ionisable valence.

(C) In the structure of copper$(II)$ sulfate pentahydrate,$[Cu(H_{2}O)_{4}]SO_{4} \cdot H_{2}O$,four water molecules are directly coordinated to the $Cu^{2+}$ ion.
The fifth water molecule is held in the crystal lattice by hydrogen bonding between the $SO_{4}^{2-}$ ion and the coordinated water molecules.

(D) According to Werner's theory,the secondary valence of a central metal ion is equal to its coordination number.
In the complex $[Co(NH_3)_4 Cl_2]^+$,the $Co^{3+}$ ion is bonded to $4$ $NH_3$ molecules and $2$ $Cl^-$ ions.
Therefore,the coordination number $= 4 + 2 = 6$.
Thus,the secondary valence of $Co^{3+}$ is $6$.

(B) To identify the complexes with bidentate ligands,we analyze the ligands present in each complex:
$a$) Tetracyanonickelate$(II)$ ion: $[Ni(CN)_4]^{2-}$. The ligand is cyanide $(CN^-)$,which is a monodentate ligand.
$b$) Trioxalatocobaltate$(III)$ ion: $[Co(C_2O_4)_3]^{3-}$. The ligand is oxalate $(C_2O_4^{2-})$,which is a bidentate ligand.
$c$) Sodium hexafluoroaluminate$(III)$: $Na_3[AlF_6]$. The ligand is fluoride $(F^-)$,which is a monodentate ligand.
$d$) bis(ethylenediamine)dithiocyanatoplatinum$(IV)$: $[Pt(en)_2(SCN)_2]^{2+}$. The ligand ethylenediamine $(en)$ is a bidentate ligand.
Thus,complexes $(b)$ and $(d)$ contain bidentate ligands.
The total number of such complexes is $2$.

(B) heteroleptic complex is one in which the central metal atom or ion is bonded to more than one type of donor group or ligand.
In $[Co(NH_3)_3(NO_2)_3]$,the central metal ion $Co^{3+}$ is bonded to two different types of ligands: $NH_3$ and $NO_2^-$.
Therefore,it is a heteroleptic complex.

(B) The oxalate ion,$(C_2O_4)^{2-}$,is a bidentate ligand.
It contains two negatively charged oxygen atoms that act as donor atoms to coordinate with the central metal ion.
Thus,it forms two coordinate bonds with the metal atom.

(A) The complex is $[Cr(CO)_6]$.
Carbonyl $(CO)$ is a neutral ligand with an oxidation state of $0$.
Let the oxidation state of $Cr$ be $x$.
$x + 6(0) = 0$
$x = 0$.
Since the oxidation state of $Cr$ is $0$,the number of electrons lost by $Cr$ is $0$.

(C) The thiocyanate ion,$SCN^{-}$,is an ambidentate ligand that possesses two potential donor atoms: nitrogen $(N)$ and sulfur $(S)$.
In any coordinate bond formation,one of these atoms acts as the donor.
Therefore,$1$ mole of $SCN^{-}$ contains $2$ moles of donor atoms.
For $2n$ moles of $SCN^{-}$,the total number of moles of donor atoms is calculated as: $2n \times 2 = 4n$ moles.

(D) The ligand $NO_2^{-}$ is an ambidentate ligand that can coordinate through either the nitrogen atom or the oxygen atom.
In either case,there is only $1$ donor atom involved in the coordination bond per molecule of $NO_2^{-}$.
Therefore,in $n$ moles of $NO_2^{-}$,the number of moles of donor atoms is $n \times 1 = n$ moles.

(D) $1$. The complex is $K[Cr(H_2O)_2(C_2O_4)_2] \cdot 3H_2O$.
$2$. Let the oxidation state of $Cr$ be $x$.
$3$. The charge on $K$ is $+1$,$H_2O$ is $0$,and $C_2O_4^{2-}$ is $-2$.
$4$. The equation is: $1 + x + 2(0) + 2(-2) = 0$.
$5$. $1 + x - 4 = 0$,which gives $x = +3$.
$6$. The coordination number is determined by the ligands attached to the central metal: $2(H_2O)$ are monodentate $(2 \times 1 = 2)$ and $2(C_2O_4^{2-})$ are bidentate $(2 \times 2 = 4)$.
$7$. Total coordination number = $2 + 4 = 6$.
$8$. Thus,the oxidation state is $+3$ and the coordination number is $6$.

(B) ligand is an ion or molecule that binds to a central metal atom or ion to form a coordination complex. The essential requirement for a species to act as a ligand is the presence of at least one lone pair of electrons to donate to the metal center.
$1$. $NO$ (Nitric oxide) has a lone pair on the nitrogen atom and can act as a ligand.
$2$. $NH_4^+$ (Ammonium ion) has all its valence electrons involved in covalent bonding with hydrogen atoms. It has no lone pair of electrons to donate,so it cannot act as a ligand.
$3$. $H_2N-CH_2-CH_2-NH_2$ (Ethylenediamine) has lone pairs on both nitrogen atoms and acts as a bidentate ligand.
$4$. $CO$ (Carbon monoxide) has a lone pair on the carbon atom and acts as a ligand.
Therefore,$NH_4^+$ is not expected to be a ligand.

(B) An ambidentate ligand is a ligand that can coordinate to a central metal atom through two different donor atoms.
$(Q) = NO_2^-$ can coordinate through $N$ (nitro) or $O$ (nitrito).
$(R) = CN^-$ can coordinate through $C$ (cyano) or $N$ (isocyano).
$(S) = SCN^-$ can coordinate through $S$ (thiocyanato) or $N$ (isothiocyanato).
$(P) = NO_3^-$ is a monodentate ligand that coordinates only through the oxygen atom and does not exhibit ambidentate behavior.
Therefore,$(P)$ is not an ambidentate ligand.

(D) An ambidentate ligand is a ligand that can coordinate to a central metal atom through two different donor atoms.
In the given list:
$P: NO_3^-$ is not ambidentate.
$Q: NO_2^-$ can coordinate through $N$ (nitro) or $O$ (nitrito),so it is ambidentate.
$R: CN^-$ can coordinate through $C$ (cyano) or $N$ (isocyano),so it is ambidentate.
$S: SCN^-$ can coordinate through $S$ (thiocyanato) or $N$ (isothiocyanato),so it is ambidentate.
Among the given options,$Q$,$R$,and $S$ are ambidentate. The combination $Q$ and $R$ is listed in option $D$.

(C) The complex is $K[Co(OX)_2(NH_3)_2]$.
$1$. Primary valency is the oxidation state of the central metal ion $(Co)$. Let the oxidation state be $x$. $1 + x + 2(-2) + 2(0) = 0$,so $x - 3 = 0$,which gives $x = +3$.
$2$. Secondary valency is the coordination number. $OX$ is a bidentate ligand (coordination number $2$) and $NH_3$ is a monodentate ligand (coordination number $1$). Total coordination number = $(2 \times 2) + (2 \times 1) = 4 + 2 = 6$.
$3$. In aqueous solution,the complex dissociates as: $K[Co(OX)_2(NH_3)_2] \rightarrow K^+ + [Co(OX)_2(NH_3)_2]^-$. This produces $1 + 1 = 2$ ions.
Thus,the values are $3, 6, 2$.

(C) The reaction with $AgNO_3$ depends on the presence of ionizable halide ions outside the coordination sphere.
$AgBr$ is a pale yellow precipitate,and $AgCl$ is a white precipitate.
In option $C$,the first complex is $[Pt(NH_3)_4Cl_2]Br_2$,which ionizes to give $2Br^-$ ions. These react with $Ag^+$ to form $AgBr$ (pale yellow precipitate).
The second complex is $[Pt(NH_3)_4Br_2]Cl_2$,which ionizes to give $2Cl^-$ ions. These react with $Ag^+$ to form $AgCl$ (white precipitate).
Therefore,the pair in option $C$ satisfies the condition.

(A) ligand with only one coordination site is called a monodentate ligand.
$O^{2-}$ is a monodentate ligand as it has only one donor atom.
$CO_3^{2-}$ (carbonate) is a bidentate ligand.
$SO_4^{2-}$ (sulfate) is a bidentate ligand.
$C_2O_4^{2-}$ (oxalate) is a bidentate ligand.
Therefore,the correct option is $A$.

(B) When a polydentate ligand binds to a metal ion through two or more donor atoms,it forms a cyclic or ring-like structure known as a chelate ring.
Such complexes are called $Chelate \ complexes$.
Therefore,the correct option is $B$.

(D) The chemical formula of Iron $(III)$ hexacyanoferrate $(II)$ is $Fe_4[Fe(CN)_6]_3$.
On ionization,it dissociates as follows:
$Fe_4[Fe(CN)_6]_3 \rightarrow 4Fe^{3+} + 3[Fe(CN)_6]^{4-}$
Total number of ions = $4 + 3 = 7$.

(C) An ambidentate ligand is a ligand that can coordinate to the central metal atom through two different donor atoms.
$SCN^{-}$ is an ambidentate ligand because it can coordinate through the sulfur atom (thiocyanato-$S$) or the nitrogen atom (isothiocyanato-$N$).
$H_2O$ is a monodentate ligand,$C_2O_4^{2-}$ is a bidentate ligand,and $[EDTA]^{4-}$ is a hexadentate ligand.

(B) In the coordination compound $[Co(en)_3]Cl_3$,the central metal atom is $Co$.
Primary valency corresponds to the oxidation state of the central metal atom. Let the oxidation state of $Co$ be $x$. Since $en$ (ethylenediamine) is a neutral ligand and $Cl$ has a charge of $-1$,we have $x + 3(0) + 3(-1) = 0$,which gives $x = +3$. Thus,the primary valency is $3$.
Secondary valency corresponds to the coordination number of the central metal atom. $en$ is a bidentate ligand,so $3$ molecules of $en$ provide $3 \times 2 = 6$ donor atoms. Thus,the coordination number is $6$.
Therefore,the primary and secondary valencies are $3$ and $6$ respectively.

(C) The primary valency corresponds to the oxidation state of the central metal ion,and the secondary valency corresponds to the coordination number.
For the complex $[Co(C_2O_4)_2(H_2O)_2]^{-}$:
Let the oxidation state of $Co$ be $x$.
$x + 2(-2) + 2(0) = -1$
$x - 4 = -1$
$x = +3$.
Thus,the primary valency is $3$.
The coordination number is the total number of donor atoms attached to the central metal ion.
$C_2O_4^{2-}$ is a bidentate ligand ($2 \times 2 = 4$ donor atoms) and $H_2O$ is a monodentate ligand ($2 \times 1 = 2$ donor atoms).
Total coordination number $= 4 + 2 = 6$.
Thus,the secondary valency is $6$.

(C) The chemical formula for ferric hexacyanoferrate$(III)$ is $Fe[Fe(CN)_6]$.
Upon ionization in an aqueous solution,it dissociates as follows:
$Fe[Fe(CN)_6] \rightarrow Fe^{3+} + [Fe(CN)_6]^{3-}$.
This results in the formation of $1$ ferric ion $(Fe^{3+})$ and $1$ hexacyanoferrate$(III)$ complex ion $([Fe(CN)_6]^{3-})$.
Therefore,the total number of ions obtained is $1 + 1 = 2$.

(B) chelating ligand is a polydentate ligand that can form a ring structure with a central metal atom.
$NH_3$ (ammine) is a monodentate ligand,meaning it binds to the central metal atom through only one donor atom.
Therefore,$NH_3$ cannot form a ring structure and is not a chelating ligand.
Oxalato,$EDTA$,and Ethane-$1, 2$-diamine are all polydentate ligands capable of chelation.

(B) The chemical formula for ammonium diammine dioxalato cobaltate$(III)$ is $(NH_4)[Co(NH_3)_2(C_2O_4)_2]$.
In this complex,the central metal ion is $Co^{3+}$.
Primary valency corresponds to the oxidation state of the metal ion,which is $3$.
Secondary valency corresponds to the coordination number of the metal ion.
The ligands are $2$ $NH_3$ (monodentate) and $2$ $C_2O_4^{2-}$ (bidentate).
Coordination number = $(2 \times 1) + (2 \times 2) = 2 + 4 = 6$.
Thus,the primary valency is $3$ and the secondary valency is $6$.

(D) ligand that possesses two different donor atoms and can coordinate with the central metal atom or ion through either of the two donor atoms is known as an $Ambidentate \ ligand$.
Examples include $NO_2^-$ (which can bond through $N$ or $O$) and $SCN^-$ (which can bond through $S$ or $N$).

(C) The oxalate ion $(C_2O_4^{2-})$ is a bidentate ligand,meaning it forms two coordinate bonds with the central metal atom.
Since there are $3$ oxalate ligands in the complex $[Fe(C_2O_4)_3]^{3-}$,the total coordination number is calculated as $3 \times 2 = 6$.

(C) homoleptic complex is a coordination compound in which all the ligands attached to the central metal atom or ion are identical.
In $K_3[Al(C_2O_4)_3]$,the central metal $Al^{3+}$ is bonded to three identical oxalate $(C_2O_4)^{2-}$ ligands.
In $[CoCl_2(en)_2]^{+}$,the central metal $Co^{3+}$ is bonded to two different types of ligands: chloride $(Cl^-)$ and ethylenediamine $(en)$. Thus,it is a heteroleptic complex.
In $K_2[Zn(OH)_4]$,the central metal $Zn^{2+}$ is bonded to four identical hydroxide $(OH)^-$ ligands.
Therefore,$K_3[Al(C_2O_4)_3]$ and $K_2[Zn(OH)_4]$ are homoleptic complexes.

(D) The coordination number of a central metal ion is the total number of sigma bonds formed by ligands with the metal atom.
In $[Fe(C_{2}O_{4})_{3}]^{3-}$,the ligand is oxalate $(C_{2}O_{4}^{2-})$,which is a bidentate ligand. Therefore,the coordination number is $3 \times 2 = 6$.
In $[Co(SCN)_{4}]^{2-}$,the ligand is thiocyanate $(SCN^-)$,which is a monodentate ligand. Therefore,the coordination number is $4 \times 1 = 4$.
Thus,the coordination numbers are $6$ and $4$ respectively.

(B) Mohr salt is a double salt with the chemical formula $FeSO_{4} \cdot (NH_{4})_{2}SO_{4} \cdot 6H_{2}O$.
When dissolved in excess water,it dissociates completely into its constituent ions:
$FeSO_{4} \cdot (NH_{4})_{2}SO_{4} \cdot 6H_{2}O \rightarrow Fe^{2+} + 2NH_{4}^{+} + 2SO_{4}^{2-} + 6H_{2}O$.
The total number of ions produced per molecule is $1 (Fe^{2+}) + 2 (NH_{4}^{+}) + 2 (SO_{4}^{2-}) = 5$ ions.

(B) ligand is defined as an atom,molecule,or ion that donates at least one pair of electrons to the central metal atom or ion to form a coordinate bond.
Since ligands donate electron pairs,they act as $Lewis$ bases.
Therefore,the essential requirement for a species to act as a ligand is the presence of at least one unshared electron pair (lone pair) that can be donated to the metal center.

(C) Ligands are species that donate at least one lone pair of electrons to the central metal atom or ion to form a coordinate covalent bond.
According to the Lewis theory,an electron pair donor is defined as a Lewis base.
Therefore,a ligand acts as a Lewis base.

(D) Bidentate ligands are those that have two donor atoms to coordinate with the central metal ion.
$1$. Cyano $(CN^-)$ is a negatively charged monodentate ligand.
$2$. Ethylene diamine ($en$ or $NH_2CH_2CH_2NH_2$) is a neutral bidentate ligand.
$3$. Acetato $(CH_3COO^-)$ is a negatively charged monodentate ligand.
$4$. Dimethyl glyoximato $(dmg^-)$ is a negatively charged bidentate ligand.
Therefore,the correct option is $D$.