Equivalence factor or n factor (Equivalent weight)

[erisedk]

Homework Statement

Equivalence factor of the salt is FeSO₄.Cr₂(SO₄)₃.24H₂O is
Ans is 8.

Homework Equations

The Attempt at a Solution

Equivalence factor of an acid or base is its basicity or acidity, and for a compound undergoing redox reaction, it is the number of electrons exchanged per mole of compound. I'm not sure how to go about in the case of the given salt.

 

[Borek]

Rather lousy question if you ask me. You can get 8 trying to precipitate hydroxides of both metals, but if you go for redox the more reasonable number is 7 (two Cr(III) get oxidized to Cr(VI) giving away 6 electrons, and Fe(II) gets oxidized to Fe(III) giving one electron, 6+1=7).

In general, equivalents are often confusing when there is more than one reaction that can take place (which is why they should be avoided in the initial chemistry lessons).

 

[erisedk]

Ok thanks!