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.

Question

Quizplus · Accepted Answer

When a compound dissociates in solution, the molar concentration of each ion is equal to the coefficient of that ion in the balanced equation. The balanced equation for the dissociation of iron(II)chloride is 
FeCl2 (s) → Fe2+ (aq) + 2Cl- (aq) 
This means that for each mole of FeCl2 that dissociates, one mole of Fe2+ ions and two moles of Cl- ions are formed. The initial concentration of FeCl2 is 0.0550 M, so the concentration of Fe2+ ions is also 0.0550 M. However, each mole of FeCl2 produces two moles of Cl- ions, so the concentration of Cl- ions is twice that of FeCl2, or 0.110 M. Therefore, the correct answer is B, 0.0550 M for the iron(II) ion and 0.110 M for the chloride ion.

The Concentration of an Aqueous Solution of Iron(II)chloride Is 0