How to calculate packing fraction or packing efficiency of two dimensional (2D) hexagonal packing solid atoms?

 Hexagonal close packing:

The particles in every next row are placed in the depressions between the particles of the first row. The particles in the third row will be vertically aligned with those in the first row. This type of packing gives a hexagonal pattern and is called hexagonal close packing

Packing efficiency calculation:

(1) One sphere will be in constant contact with 6 other spheres hence coordination number is 6

(2) Side of hexagon is a and a=2r where r is the radius of atom (sphere) .

(3) Area of hexagon unit cell is 6*area of six equilateral triangles 

       (4) Area of atoms in the hexagon unit 

      Packing fraction (PE) , fraction of area occupied by spheres 

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

Boric acid is a weak monoprotic acid (Ka=6.4×10⁻¹⁰).Therefore, it cannot be directly titrated with standard strong alkali (NaOH). But by the addition of an organic poly hydroxy compound such as 1,2- or 1,3-diol, (Like Sugar, Mannitol, Catechol)  it is converted to a much stronger acid, which can be titrated using phenolphthalein. This is due to the complex formation between hydrated borate ion and either 1,2- or 1,3-diol  for example .

Ploy hydroxy (Cis-diol) increases acidity of boric acid due to formation of complex with metaborate and reaction goes to farward to produce more H⁺.

What is Urotropine give the structure and uses of Urotropine?

Urotropine is nitrogen containing bicycling Compound it's chemical name is Hexamethylenetetramine which is formed by reaction of formaldehyde with ammonia. Urotropine is used as urinary antiseptic.

It is also used for preparation of Cyclonite Research and Development Explosive(RDX).

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Although anti conformation is more stable than the gauch conformation but in some cases gauch or skew conformation is more stable than the anti confirmation why?

Gauch or skew conformation is more stable than the anti because of the intramolecular hydrogen bonding which is geometrically possible only in the gauch conformation.

For examples:

Ethane-1,2-diol, 2-Fluoroethan-1-ol, 2-chloroethan-1-ol and 2-Aminoethanol etc.
2-chloroethane-1-ol:

Ethane-1,2-diol:

Realated Questions:

How many cyclic isomers possible of (C6H12) Hexene?

How many cyclic isomers possible of (C5H10) pentene?

Write the major and minor product of hydration of 1-Methylcyclopent-1-ene in acidic medium?

Why enol form of Beta Dicarbonyl compound more stable than those of monocarbonyl compounds?

Why enol form of phenol is more stable than its keto isomers?

What is fries rearrangment acylation ?

Conversion of phenolic esters of aliphatic and aromatic carboxylic acids into ortho- and para-acylphenols in the presence of FCR catalyst (AlCl3). Is know as Fries rearrangement.

Related questions:
What is difference between Houben–Hoesch acylation reaction and Gatter- mann–Koch formylation reaction? 

More reated Questions:

Penta-1,3-diene is more stable than penta-1,4 -diene. Why?

Phenoxide ion is more stable than an alkaoxide. why?

Why does aqueous sodium bicarbonate solution dissolve carboxylic acids but not phenol though they are also acidic ?

Why enol form of Beta Dicarbonyl compound more stable than those of monocarbonyl compounds?

Why enol form of phenol is more stable than its keto isomers?

Reactivity order of Pyrrole, Furan and Thiophene towards Electrophilic substitution :

Phenyl group is known to extract negative inductive effect, but each phenyl ring in biphenyl is more reactive than benzene towards Electrophilic substation. Why?

Chloroform is more acidic than fluoroform why?

Fluorine is more electronegative than chlorine even then, p-flurobenzoic acid is weaker acid than p-chlorobenzoic acid explain ? 

Trifluoroethyl carbocation is less stable than trifluromethyl carbocation why ?

Why is the Tropylium carbocation less stable than the tricyclopropylmethyl carbocation?