Question

The third cell contained an electrolyte of a trivalent ion, X⁺³. The cathode in this cell was weighed before and after the formation of the hydrogen gas. It was found that 0.06287 g of X had formed.

a.         Calculate the equivalent mass of X

b.         Considering the most common charges of metal ions and the probability of small errors, what is a likely identity of metal X? Justify your answer!

Answer 1

Considering is a trivalent ion, it's equivalent mass is calculated by dividing it's obtained mass between it's ion, so:

0.06287/3 = 0.02096 g/eq.

However, the correct way to do this is using the molar mass (molecular weight) of this ion. But in this case we don't know which metal this is, so we use the mass formed.

Considering the metal with these charges (3+) we have the following:

Fe, Ni, Co, Mn, Al, and Au are the most common (and actually the more used), the likely identity of the metal would be Aluminium (Al) or even the Au, because these are the elements that actually acts as a reducting agents (oxidates another metal) and that's why they are put in the cathode. the other elements can act as a reducting and oxidating agents too, but the aluminium is a really well reducting agent. So it's probably the identity of this metal.