Question

preparation of tetraethylammonium tetrachloromanganate(II) [C2H5)4N]2[MnCl4]

a)AgCl is insoluble in water and nitric acid but it is soluble in ammonia why?

b)the following redox reaction describe the first reaction step of test for Mn.

2Mn2+ + 5S2O8 2– + 8H2O →2MnO4¯+10SO42¯+16H+

what are the roles of each?

a)MnO4-

b)SO4 2-

c)H2O

d)S2O8 2-

e )Mn 2+

Answer 1

a)AgCl is insoluble in water and nitric acid but it is soluble in ammonia, because

In ammonia (NH3) forms complex with Ag+ ion of AgCl

i.e. AgCl + 2 NH₃ -------> [Ag(NH₃)₂]⁺ Cl^-

This complex is soluble in polar ammonia solvent and hence the solubility of AgCl in the NH3 ammonia.

Such complex formation is not possible in water and in nitric acid and hence AgCl is insoluble in water (H₂O) and Nitric acid (HNO₃).

=============xxxxxxxxxxxxxxxxxxxxx=======================

b) The following redox reaction describes the first reaction step of test for Mn.

2Mn²⁺ + 5S₂O₈^2– + 8H₂O →2MnO₄¯+10SO₄²¯+16H⁺

The reverse of above reaction is,

2MnO₄¯+10SO₄²¯+16H⁺ ------ > 2Mn²⁺ + 5S₂O₈^2– + 8H₂O

Roles of various species in the overall reaction,

a)MnO₄^- reduces to Mn²⁺ for formation of MnCl₄

b)SO₄^2- get oxidized to S₂O₈^2– i.e.it reduces MnO₄^2- to Mn²⁺

c)H₂O – Provide necessary H⁺ and OH^‑ for the reaction. And provide a medium for reaction.

d)S₂O₈^2- - It’s a oxidized form of SO₄^2-

e )Mn²⁺ - It is the species which oxidizes Ag to Ag⁺ for complexation with amine.

==================xxxxxxxxxxxxxxxxxxxxxxxx=======================