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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