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which are the most important reactions that one should surely know in d-block elements?

Asked by Komal Vaishnav 24th February 2015, 6:02 PM
Answered by Expert
Answer:

Hi,

Important reaction from d-block elements are as follows:

It is prepared by fusion of chromate ore (FeCr2O4) with sodium carbonate in excess of air.

4FeCr2O4 + 8Na2CO3 + 7O2  rightwards arrow 8Na2CrO4 + 2Fe2O3 + 8CO2 

2Na2CrO4 + H2SO4 rightwards arrow Na2Cr2O7 + H2O + Na2SO4

Sodium                                Sodium

chromate                             dichromate

Na2Cr2O7 + 2KCl rightwards arrow K2Cr2O7 + 2NaCl

Effect of pH on chromate and dichromate ions: The chromates and dichromates are interconvertible in aqueous solution depending upon pH of the solution. The oxidation state of chromium in chromate and dichromate is the same

2 CrO42- + 2H+ rightwards arrow  Cr2O72- + H2O

Cr2O72- + 2 OH- rightwards arrow2 CrO42-+ H2O

  1. Potassium dichromate acts as a strong oxidizing agent in acidic medium.

Cr2O72- +14 H+ + 6e- rightwards arrow 2 Cr3+ + 7 H2O

 

  1. Potassium permanganate acts as a strong oxidizing agent in acidic, neutral or faintly basic medium.

In acidic medium.

MnO4- + 8 H+ + 5 e- rightwards arrowMn2+ + 4 H2O

In neutral or faintly basic medium,

MnO4- + 3 e- + 2 H2O rightwards arrow MnO2 + 4OH-

Answered by Expert 24th February 2015, 6:56 PM
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