Two voltameters, one having a solution of silver salt and the other of a trivalent-metal salt, are connected in series and a current of 2A is maintained for 1.50 hours. It is found that 1.00g of the trivalent metal is deposited.

(a) What is the atomic weight of the trivalent metal?


(b) How much silver is deposited during this period? Atomic weight of silver is 107.9 g mol–1.



Given-
Mass of salt deposited, m = 1 g



Current, i = 2 A



Time, t = 1.5 hours = 5400 s


Atomic weight of silver is 107.9 g mol–1.


For the trivalent metal salt



Equivalent mass = 13 times its Atomic weight



The E.C.E of the salt


Z=Equivalent mass


96500=Atomic weight 3×96500


(a) Using the formula, from faraday’s law of electrolysis –



where,


m = the mass of the substance deposited on the electrode


z=electrochemical equivalence


i=current passing


t=time taken


Now, 1 gram is deposited and the element is trivalent metal






(b)Now the relation between equivalent mass and mass deposited on plates is given by –



Where


E1 is the equivalent mass of the trivalent metal


E2 is the equivalent mass of the silver


m1 is the mass of trivalent material deposited


m2 is the mass of the silver deposited


Atomic weight of silver is 107.9 g mol–1.


Substituting to calculate the mass deposited –




1