Question

The concentration of an aqueous solution of iron(II) chloride is 0.0550 M. What is the molarity of each ion in this solution?

A.	0.0550 M for both the iron(II) and chloride ions.

B.	0.0550 M for the iron(II) ion and 0.110 M for the chloride ion.

C. 0.110 M for the iron(II) ion and 0.0550 M for the chloride ion.

D. not enough information is given to determine each molarity.

Answer 1

The dissolution reaction of iron(II) chloride in water is

   (1)

From the above equation, it is evident that 1 mol iron(II) chloride upon dissolving produces 1 mol iron(II) or ferrous ion and 2 mol chloride ions.

Here, the concentration of iron(II) chloride is 0.055 M.

Therefore, 1 L of the solution contains 0.055 mol of iron(II) chloride. And from equation (1), we can see the stoichiometry of the reaction to be that 1 L of the solution contains 0.055 mol ferrous ion and 0.110 mol chloride ion.

Now since the volume of the system does not change upon dissolution of the salt, the concentrations of the ferrous ion will be 0.055 M and that of the chloride ion will be 0.110 M.

So the answer will be option B.