Question #d46e7

1 Answer
Oct 2, 2017

MCl3

Explanation:

The trick here is to realize that the number of moles of electrons needed to reduce 1 mole of M?+ cations will give you the net charge of the metal cations.

In your case, you know that 3 moles of electrons will reduce the M?+ cations to 1 mole of M metal, so you can say that

M?+(l)+3eM(s)

As you know, in any chemical reaction, charge must be conserved.

Since the metal is reduced to its elemental form, i.e. the charge on the metal will be 0, you can say that you have

(?+)+3()=0

This implies that

?=3

Therefore, your unknown chloride contained 3+ metal cations. Since chlorine forms 1 anions, i.e. the chloride anion, Cl, you can say that the empirical formula of the chloride will be

[M]3++3[Cl]MCl3

This tells you that you need three 1 chloride anions to balance the overall 3+ positive charge of a single M3+ cation.