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Thursday, April 28, 2022

Coordination Compounds or complex:

8.1 Double salt or lattice salts
8.2 Coordination or complex salts
8.3 Structure and terminology
8.4 Nomenclature of complex compounds
8.5 Type of ligands
8.5 Special ligands
8.6  Bonding  in complexes:
8.6.1(A) Werner's theory of coordination complexes:



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Tuesday, April 26, 2022

Banana Bond or 3C-2e Bond or Bridge bond or structure of B2H6 and Al2(CH3)6:

(1) Formation of 3C-2e bond in B2H6 is best explain by MOT and total number of bond in B2H6 is 6 (3C-2e=2 and 3C-4e=4)

(2) Bridge bonds are longer than terminal bond because at bridge bonds electrons are delocalized at three centres
(3) Bond energy (441kj/mole) of B-H-B bond is greater than bond energy (381 K j/mole) of   B-H bond.
(4) Hybridization of B atom is sp3, so non planer, and non polar (U=0)
(5)  B2H6 Methylated up to B2H2 Me4
(6) B2H6 is hypovalent molecule hence act as Lewis acid and undergoes two type of cleavage when react with Lewis base:

(A) UNSYMETRICAL CLEAVAGE: 
B2H6 Undergo unsymmetrical cleavage with small size strong Lewis base like NH3 NH2Me and NH (Me) 2 etc.

(B) SYMETRICAL CLEAVAGE:
B2H6 undergoes symmetrical cleavage with large size weak Lewis base like PH3, PF3,Me3N , OEt , OMe3, pyridine , THF , Thiophene , SMe2 ,Set2

Related Questions: 

(1) Why aqueous solution of AlCl3 is acidic in nature ?

(2) What happen when aq AlCl3 react with Acid or Base?

(3) Although anhydrous aluminium chloride is covalent but its aqueous solution is ionic in nature. Why?

(4) Why BF3 do not exist as dimer?. Explain.

(5) Why B-F bond length in BF3 is shorter (130 pm) than B-F bond Iength in BF4- (143 pm)?. Explain.

(6) B-F bond length in BF3 is shorter than B-F bond length in (BF4)- why?

(7) When B2H6 is allowed to react with following Lewis bases, then how may given Lewis base form adduct through symmetrical Cleavage of B2H6.

(8) What is product of reaction between diborane (B2H6) and ammmonia (NH3)?

(9) Why methylation of Diborane (B2H6) replace four hydrogen only ?

(10) What is Use of Boric Acid?

(11) What is use of Orthoboric acids?

(12) What is basicity of "Boric acid" ?

(13) Why Boric acid exist in solid state ?

(14) What is structure of solid Ortho Boric acid ?

(15) What is effect of heat on Borax?

(16) What is the structure of trimetaboric acid and trimetaborate ion?

(17) What is the Sodium per borate ,give the structure and its uses?

(18) Why aqueous solution of borax reacts with two moles of acids ?

(19) What is the molecular formula of Borax ?

(20) Why Boric acid become strong acid in the presence of cis 1,2-diol or 1,3-diol ?

(21) Why Borazine is more reactive than benzene towards Electrophic Aromatic substitution reactions ?

(22) Why Borazine (B3N3H6) is also known as inorganic benzene ?.

(23) Four-center two-electron bond (4C-2e Bond): Structure of AlCl3:

(24) What is the difference between the structure of AlCl3 and diborane?

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Monday, April 25, 2022

What is the structure and structural characteristic of dichromate kon (Cr2O7)-2?

The whole molecule dichromate ion (Cr2O7)-2 is non planer and polar and oxygen atom of (Cr-O-Cr) oxy-linkage does not involve in delocalization due to maximum repulsion hence two Cr-O bond have equal length and bond order may be/equal to one while other six Cr=O bond have eqaual bond length.


In dichlorine heptaoxide (Cr2O7)-2 , two (CrO4 )-2 group connected with an oxygen atom which is sp3 hybridised (non planer) and bond angle may be expected 109⦁28’ but actually due to the presence of two lone pair on oxygen atom the Cr-O-Cr bond angle deviated from ideal and it may be greater (119⦁) than ideal bond angle.

What is the structure and structural characteristic of dichlorine heptaoxide (Cl2O7)-2?

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Sunday, April 24, 2022

14th Group: Carbon Family:

(A) Silicon compounds:

Illustrative Examples:

(B) Carbon Allotropes and compounds:


Illustrative Examples:




(7) Buckminsterfullerene: Bucky Balls: Allotrope of Carbon:

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Compare the splitting energy (∆●) into the following compound and give appropritate reason ?

Given compounds are...
(A) [Co(NH3)6]3+ 
(B) [Rh(NH3)6]3+
(C) [Ir(NH3)6]3+
Solution :
In given compounds number of ligands, types of ligands and oxidation state is same for central atom belongs to same group but different transition series 3d, 4d and 5d respectively. We know that as move top to bottom size of d-orbital(3d--> 4d --> 5d) is increases so ligand approches to d-orbitals more closely so the repulsion
between d-orbital of metal and ligand is high and splitting energy increases.order of splitting energy [Co(NH3)6]3+ < [Rh(NH3)6]3 <[Ir(NH3)6]3+

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Explain the formation of Na4[Fe(CN)6] and Na4[FeF6] ? Show which is low spin and which is high spin complex and also calculate the Crystal field stablisation energy (CFSE) ?

In the given compounds CN– is strong field ligands and F– is weak field ligand and in both compounds ions is in +2 oxidation state d6 configuration.
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What are bridging ligands and how to show bridging ligands in naming, explain with suitable example.

(A) If a complex ion has two or more than two metal atoms then it is termed polynuclear. The ligand which connects the two metal ions is called as Bridging ligand or Bridge group.
(B) A prefix of Greek letter (U) , is repeated before the name of each different kind of bridging group.
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Friday, April 22, 2022

[Fe(CN)6]3- is weakly paramagnetic while [Fe(CN)6]4- is diamagnetic, why ?


[Fe(CN)6]3- involves  d2sp3  hybridization

Related Questions;

(1) What are pi-donors ligands give the examples?


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[Fe(CN)6]4- is diamagentic while [FeF6]4- is strongly paramagnetic.Why ?

CN- is strong field ligand and so it pairs up the electrons leading to the formation of low spin complex which is diamagnetic. [Fe(CN)6]4-
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Which of the Complex of the following pairs has the largest value of CFSE?


(1) [Co(CN)6]3-  and [Co(NH3)6]3+
(2) [Co(NH3)6]3+ and [CoF6]3-
(3) [Co(H2O)6]3+  and [Rh(H2O)6]3+
(4) [Co(H2O)6]2+ and [Co(H2O)6]3+

SOLUTION:

(1)  CN is the stronger ligand than NH3 therefore CFSE of [Co(CN)6]3-  will be more than  [Co(NH3)6]3+
(2) NH3 is stronger ligand than F therefore CFSE of [Co(NH3)6]3+ will be more than [CoF6]3- .
(3) Co belong to 3d series whereas The Rh belong to 4d series. More the value of n more is CFSE therefore CFSE of  [Rh(H2O)6]3+  is more than [Co(H2O)6]3+ .
(4) Oxidation number of Co in [Co(H2O)6]3+ is more than the Oxidation number of [Co(H2O)6]2+  therefore, CFSE of [Co(H2O)6]3+ is more than  [Co(H2O)6]2+ .


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Saturday, April 16, 2022

Compare the splitting energy (CFSE) into the following compound and give appropritate reason ? [Co(NH3) 6] 3+ , [Rh(NH3) 6] 3+,[Ir(NH3) 6] 3+

In given compounds number of ligands, types of ligands and oxidation state is same for central atom belive to same group but different transition series 3d, 4d and 5d respectively. We know that as move top to bottom size of d-orbital(3d--> 4d -->5d) is increases so ligand approches to d-orbitals more closely so the repulsion between d-orbital of metal and ligand is high and splitting energy increases. 
Thus order of splitting energy 
[Co(NH3)6]3+ < [Rh(NH3)6]3+ < [Ir(NH3)6]3+

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Which is correct statement for regarding I2Cl6 molecule?

(A) The molecule is planar
(B) 8 Number of angles of type 02 are present
(C) 03 > 01 > 02
(D) Total 4 unshared lone pairs are present
Ans key (A)
What is structure and also explain the bridge bonding of I2Cl6 ?

Related Questions:

(1) What is the difference between the structure of AlCl3 and diborane?

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Thursday, April 14, 2022

Ellingham Diagram and it's features:


The changes in Gibbs energy that occur when one moleofoxygen isused may be plotted against temperature for a number of reaction of metals to form
their oxides. Such a graph is shown in Figure below and is called an Ellingham diagram for oxides. Similarly, we can plot Ellingham diagrams for halides.
The Ellingham diagram for oxides show the following important features :
(1) Ellingham diagram normallyconsist of plots of dfG° vs T for the formation of oxides of elements, i.e. for the reaction.
(2) The graphs for metal oxide all slope upwards because the change in Gibbs energybecomes less negative with increase in temperature.
(3) Each plot follows a straight line unless there is some change in phase.
(4) When the temperature is increased, a point will be reached when the line crosses dG = 0 line. Below this temperature the dfG° of oxide is negative and hence the oxide is stable.Above this temperature dfG° of the oxide is positive and hence the oxide becomes unstable and decomposes on its own into metal and oxygen.
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Hall Heroult process : Electrolytic refining of Alumina ore of Aluminium:

Electrolysis of fused Alumina.
Cathode : Iron-tank lined with carbon bricks
Anode : carbon
Electrolyte : Molten [Al2O3
(5%) Na3AlF6 (85%) + CaF2 (5%) + AlF3 (5%) ]
O2 is liberated at anode and Al collects at the bottom.


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Hoope’s refining process used for electrolytic refining of Aluminium:

Cathode : carbon electrodes
Anode : Fe tank lined with carbon bricks
Electrolyte : Na3AlF6 + BaF2
Bottom layer : Impure aluminium consists of Cu, Si etc in molten state.
Middle layer : molten mixtureof Fluorides of Na, Ba,Al andAl2O3
Top layer : pure molten aluminium.
On passing the current, Al is deposited at cathode from the middle layer and an equivalent amount of Al from the bottom layer moves into the middle layer leaving behind the impurities.

Chemical refining methods:
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Wednesday, April 13, 2022

Is oxalate (C2O4)2- Weak field ligand or strong field ?


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Although [Fe(CN)6]4- is more stable (EAN-36) than [Fe(CN)6]3-(EAN-35) as par EAN rule but actually [Fe(CN)6]3 is more stable than [Fe(CN)6]4- ?

Although [Fe(CN)6]4- is more stable (EAN-36) than [Fe(CN)6]3-(EAN-35) as par EAN rule but actually  [Fe(CN)6]3 is more stable than  [Fe(CN)6]4- because in  Fe+3  Zeff will be more hence bonding between Fe+3 and -CN is more effective.

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Which complex is more stable [Ni(CN)4]4- or [Ni(CN)4]2- and why?

In general stability of Complexes is directly proportional to the magnitude of charge on central metal atom. Thus Complexes of Ni +2 are more stable than Ni0

[Ni(CN)4]4- < [Ni(CN)4]2- 

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d3s Hybrization and it's examples.

d3s Hybridization or dxy+dyz+dxz+s  possess tetrahedral geometry  and bond angle 109'28'. And examples are as CrO2Cl2,  CrO42-, MnO41-, MnO42-
VO43-, Cr2O72-

HYBRIDISATION AND GEOMETRY:
Related Questions;

(1) What type of ligands are known ?

(6) What are the chemical formula and chemical name of Glauber salt ?

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Chemical methods of purification/refining of metals:

These methods include the following methods :
(1) OXIDATIVE REFINING :
The method is used when the impurities present in the metal have a greater affinity for oxygen and are more readily oxidized than the metal. Then these oxides may be removed as follows 

(A) These oxide may form a scum on the surface of the metal. This scum can easily be removed by
skimming.
(B) If the oxides are volatile, they escape from the mouth of the furnace.
(C) The oxides may form a slag with the lining on the inside surface of the furnace and may thus be removed. In the formation of the slag, the lining acts as a flux.This method is usually employed for refining metals like Pb, Ag, Cu, Fe, etc. In this method the molten impure metal is subjected to oxidation by various ways.
(6) Vapour phase refining:

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Pudding process : Used for the manufacture of wrought iron from cast iron:

This process is used for the manufacture of wrought iron from cast iron. We know that cast iron contains the impurities of C, S, Si, Mn and P. When these impurities are removed from cast iron, we get wrought iron. In this process the impurities are oxidised to their oxides not by blast of air but by the haematite (Fe2O3) lining of the furnace.


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Vapour phase refining : Van Arkel–De Boer process :

Small amounts of very pure metals (Ti, Zr, or Bi) can be produced by this method. This process is based on the fact that iodides are the least stable of the halides. The impure element is heated with iodine, producing a volatile iodide, TiI4, ZrI4, or BiI3. These are decomposed by passing the gas over an electrically heated filament of tungsten or tantalum that is white hot. The element is deposited on the filament and the iodine is recycled. As more metal is deposited on the filament, it conducts electricity better. Thus, more electric current must be passed to keep it white hot. Thus the filament grows fatter and eventually the metal is recovered. The tungsten core is distilled out of the center and a small amount
of high purity metal is obtained.

Impure Ti + 2I2 (50–250ºC)-->TiI4 Tungsten filament(1400ºC)-->Ti+ 2I2

The method is very expensive and is employed for the preparation of very pure metal for specific use.

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Vapour phase refining : Mond's process:

Extraction of Nickel (Mond's process) : Nickel is extracted from sulfide ore by roasting followed by reduction with carbon, but the
process is complicated by the fact that nickel is found in association with other metals. The refining is rather unusual, for nickel forms a complex with carbon monoxide
tetracarbonylnickel(O) [Ni(CO)4]. This substance is molecular in molecular in structure and readily volatilized (boiling point 43ºC). It is made by heating nickel powder to 50ºC, in a stream of CO and then decomposed at 200ºC. Any impurity in the nickel sample remains in the solid state and the gas is heated to 230ºC, when it decomposes, giving pure metal and CO, which is recycled. Ni(CO)4 is gaseous and may be produced by warming nickel with
CO at 50ºC.

The sequence of reaction is

 H2O(g) + C +-> CO(g) + H2

Ni(s) + 4 CO(s)-->(50ºC) [Ni(CO4)](g)
[Ni (CO)4](g) (200ºC )--> Ni + 4CO(g)

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Electrolytic refining process : used for Cu , Ni and Al :

Some metals such as Cu, Ni, and AI are refined electrolytically. 

(1) The Hooper process is a process for the electrolytic refining of aluminum. Impure AI forms the anode and pure AI forms the cathode of the Hooper's cell which contains three liquid layers. The bottom layer is molten impure AI, the middle is a fused salt layer containing aluminum fluoride, and the top layer is pure AI. At the anode (bottom layer), AI passes with solution as aluminum ion (AI3+), and at the cathode (top layer), these ions are reduced to the pure metal. In operation, molten metal is added to the bottom of the cell and pure aluminum is drawn off the top.

At anode : AI --> AI3+ + 3e–
At cathode : AI3+ + 3e– --> AI


(2) Copper obtained from the reduction of ores must be purified for use in making electrical wiring
because impurities increase its electrical resistance. The method used is electro-refining. Impure Cu obtained from ores is converted to pure Cu in an electrolyte cell that the impure copper as the anode an pure copper as the cathode. 
The electrolyte is an aqueous solution of CuSO4. At the impure Cu anode, Cu is oxidized along with the more easily oxidized metallic impurities such as Zn and Fe. The less easily oxidized impurities such as Ag, Au, and Pt fall to the bottom of the cell as anode mud, which is reprocessed to recover the precious metals. At the pure Cu cathode, Cu2+ ions get reduced to pure copper metal, but the less easily reduced metal ions (Zn2+, Fe2+, and so forth) remain in the solution.

Anode (oxidation) : 
M (s) --> M2+ (aq) + 2e– (M = Cu, Zn, Fe)
Cathode (reduction) :
 Cu2+ (aq) + 2e– --> Cu(s)

Thus, the net cell reaction simply involves transfer of Cu metal from the impure anode to the pure
cathode, Cu obtained by this process is 99.95% pure.

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