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Grade Upto college levelPhysical Chemistry

A battery is constructed of Cr and Na2Cr2O7. The unbalanced chemical reaction when such a battery discharges is following :

Na2Cr2O7 + Cr + H+ gives Cr3+ +H2O + Na+

If one Faraday of electricity is passed through the battery during the charging, the number of moles of Cr3+ removed from the solution is :

Profile image of Karan
12 Years agoGrade Upto college level
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1 Answer

Profile image of Vineeth Krishna T
12 Years ago

The balanced equation is 

Na2Cr2O7 + 2Cr + 14H+ →  3+ + 7H2O + 2Na+ 

Number of moles of electrons exchanged=6.

3 moles of electrons(3 faraday of elec.) reduce 1 moles of Cr3+ to Cr.

Thus, 1 mole of electrons consumes 1/3=.33 moles of Cr3+.