Ncert Solutions Chemistry Class 12th

(i) Tetrahydroxidozincate (II) = [Zn (OH)₄]^-2

Tetrahydroxi means 4 hydroxide ions with zinc in + 2 oxidation state. Hydroxide ions have a negative charge of -1, so balancing the overall charge of the coordination compound to be zero we get the formula as : [Zn (OH)₄]^-2

(ii) Potassium tetrachloridopalladate (II) = K₃ [PdCl₄].

Tetrachlorido means 3 Chloride ions each having a negative charge. Platinum is in + 2 state. Balance overall charge as 0, no. Of potassium ions are 3. Formula: K₃ [PdCl₄].

(iii) Diamminedichloridoplatinum (II) = [Pt (NH₃)Cl₂]²⁺

Diammine means 2 ammonia molecules, dichlorido means 2 chloride ions, platinum in + 2 state. Formula: [Pt (NH₃)Cl₂]²⁺

(iv) Potassium tetracyanidonickelate (II) = K₂ [Ni (CN)₄].

tetracyanido means 4 cyanide ions each with a unit negative charge and nickel atom with + 2 state. Formula: K₂ [Ni (CN)₄].

(v) Pentaamminenitrito-O-cobalt (III) = [Co (ONO) (NH₃)₅]⁺²

penataammine means 5 ammonia molecules, nitrito-O means nitrate ion which is bonded to central atom via oxygen and cobalt in + 3 state. Formula: [Co (ONO) (NH₃)₅]⁺²

(vi) Hexaamminecobalt (III) sulphate = [Co (NH₃)₆]₂ (SO₄)₃

Hexaammine means six ammonia molecules and cobalt in + 3 state. Sulphate have a negative charge of-2 Balance overall charge as 0. Formula: [Co (NH₃)₆]₂ (SO₄)₃

(vii) Potassium tri (oxalato)chromate (III) = K₃ [Cr (C₂O₄)₃].

trioxolato means 3 oxolate ions and chromium in + 3 state. Balance overall charge as 0. Formula: K₃ [Cr (C₂O₄)₃].

(viii) Hexaammineplatinum (IV) = [Pt (NH₃)₆]⁴⁺

hexaammine means 6 neutral ammonia molecules and platinum in + 4 state. Balance overall charge as 0. Formula: [Pt (NH₃)₆]⁴⁺

(ix) Tetrabromidocuprate (II) = [Cu (Br)₄]^2-

tetrabromido means 4 bromide ions with a unit negative charge each and copper in + 2 state. Balance overall charge as 0. Formula: [Cu (Br)₄]^2-

(x) Pentaamminenitrito-N-cobalt (III) = [Co (NO₂) (NH₃)₅]²⁺

pentaammine means 5 neutral ammonia molecules, nitrito-N means nitro group bonded to central atom via the lone pair of electron of nitrogen and cobalt in + 3 state. Balance overall charge as 0. Formula: [Co (NO₂) (NH₃)₅]²⁺

(i) Let Oxidation of Co be x and charge on the complex is given as + 2

H₂O has Oxidation Number: 0

CN has Oxidation Number: -1

en has Oxidation Number :0

 

(ii) Let Oxidation number of Co be x and charge on the complex is given as + 1

Br has Oxidation number: 1

en has oxidation number : 0

 

(iii) Let Oxidation number of Pt be x and charge on the complex is given as -2

Cl has oxidation number : -1

 

(iv) This complex can also be seen as [Fe (CN)₆]^3-

Let Oxidation number of Fe be x and charge given on the complex is given as -3

CN has oxidation number : -1

(v) Let Oxidation number of Cr be x and charge given on the complex is given as 0

NH₃ has oxidation number : 0

Cl has oxidation number: -1

Ligands are the neutral or negatively charged entities surrounding the central metal atom of the coordination complex which possesses at least one unshared pair of electrons.

Based on the number of donor sites of these ligands, Ligands are classified as:

Unidentate ligands: These Ligands which have only one donor site are called unidentate ligands.

Example: F^-, Cl ^– etc.

Didentate ligands: These Ligands which have only two donor site are called didentate ligands.

Example: Ethane-1,2-diamine, Oxalate ion etc.

Ambidentate ligands: These ligands which can attach them with the central metal atom by two different atoms are called as ambidentate ligands.

14.33

The different types of RNA found in the cell are listed below:-

(i) Messenger RNA (m-RNA)

It carries the genetic message code from the DNA to ribosomes. It is produced by the DNA; m-RNA is also single stranded and constitutes about 15% of total RNA.

(ii) Ribosomal RNA (r-RNA)

It is found in the ribosomes and it is usually associated with protein to form the ribosomes. It is synthesised in the nucleus by DNA. It is single stranded, comprising about 80% of total RNA. It is metabolically stable.

(iii) Transfer RNA (t-RNA)

It is synthesised in nucleus by DNA. It is also called soluble RNA. It is single stranded. There are 20 different kinds of t-RNA and each type has specificity for a particular amino acid. It constitutes about 5% of total RNA. It has very short life.

(1) Coordination Entity: Coordination entity is a charged entity having positive or negative charge in which the central atom is surrounded by molecules which may be neutral/negatively charged called Ligands

Examples:

i. Cationic Complexes: [Cu (H₂O)₆]²⁺, [Al (H₂O)₆]³⁺

ii. Anionic Complexes: [CuCl₄]^2-, [Al (H₂O)₂ (OH)₄]^-

iii. Neutral Complexes: [Co (NH₃)₄ Cl₂], [Ni (CO)₄]

(2) Ligands: Ligands are the neutral or negatively charged entities surrounding the central metal atom of the coordination complex which possesses at least one unshared pair of electrons

Example: F^-, Cl^-, Br^-, I^-, H₂0, and NH₃

(3) Coordination Number: Coordination Number which is also called as Ligancy is the total number of ligands that are attached to the central metal atom of the coordination

Example: [Cr (NH₃)₂Cl₂Br₂]^? has Cr³⁺ as its central cation, and has a coordination number of 6

Al³⁺ has coordination number 4 in [AlCl₄]^- but 6 in [AlF₆]^3-.

(4) Coordination polyhedron: Coordination polyhedron is defined as the spatial arrangement of the ligands around the central atom of a coordination

Example:

In the figure: The pink Sphere depicts the central atom of the coordination entity.

(5) Homoleptic complexes: Complexes in which the central metal atom is surrounded only by the same kind of donor groups which are the ligands.

Example: [Ag (CN)₂]^-, [Fe (CN₆)]⁴⁺ etc.

(6) Heteroleptic complexes: Complexes in which the central metal atom is surrounded by more than one kind of donor groups which are the ligands.

Example: [Co (NH₃)₄ Cl₂] ⁺, [Co (NH₃)₅ Cl]²⁺