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Tuesday, November 10, 2020

What is "Nascent" Hydrogen ?

Hydrogen is more receive than dihydrogen at the time of preparation. The Hydrogen produced in situ in contact with the substance to be reduced is known as "Nascent" hydrogen.

What is "Pure Gold" ? and what is meaning of " carat" with related to the purity of gold ?

Purity of ornamental gold is expressed in term of the "carat" and "24 carat gold" is 100%  pure on carat scale .
We know that 100%  gold is very soft so that not suitable for making ornaments then increases hardness of gond by adding silver or copper to make ornaments. Thus find the percentage of gold is "x" carat gold the % of gold and copper calculated as:
% of of gold in "20 carat gold" = 20/24×100= 83.33%

Melals like Cu, Ag, Zn, Hg and Pb occur in nature as sulphide rather than oxides. Why ?

The cations of these metals i.e. Cu+2, Ag+, Zn+2, Hg+2 (pseudo inert gas configuration), and Pb+2 ( inert gas configuration) have high polarising power and hence can easily polarise the bigger S-2 ion than the smaller O-2 ion. Hence sulphides are more stable than oxides of these metals.
Cu+2, Ag+, Zn+2 and Hg+2 are soft Lewis acids and S-2 is soft Lewis base . Compounds obtained by reaction between soft Lewis acid and soft Lewis base is stable. O-2 is hard Lewis base . Adduct of soft Lewis acid and hard Lewis base is not very stable compounds.
 

Saturday, November 7, 2020

Why halogens are insoluble in water ?

Halogens (X2) are "non polar" in nature , they are insoluble in water (polar solvent) but in soluble in non polar solvents  like CCl4, C6H6, and CS2 etc.
(1): But Fluorine is soluble in water due to its high oxidizing nature, decomposition even water and form ozonides oxygen.
(2): To increase the solubility of Iodine in water, potassium iodide (KI) is added


Why alums are used as Mordant in dyeing ?

Alums are used as Mordant in dyeing because when fabric to be dyed in dipped a solution of alum and heated with steam. Hydrolysis of [Al(H2O)6]+3 deposite Al(OH)3 into the fibres of materials and the dye is adsorbed on the Al(OH)3.