Question

Iron fluoride (FeF2) dissociates according to the following equation: FeF2(s) ⇌ Fe2+(aq) + 2 F–(aq) A sample of iron fluoride (FeF2) is dissolved in water, and a saturated solution is obtained. The [Fe2+] is measured to be 2.05 × 10–4 mol/L. What is the concentration of fluoride (F–) ions?

Answer 1

Answer:

4.1 x 10^-4 mol/L

Explanation:

For the equation

FeF2(s)  --> Fe2+(aq) + 2F- (aq)

We have that for every mole of FeF2 we have a mole of Fe2+ and 2 moles of F-

FeF2(s)  --> Fe2+(aq) + 2F- (aq)

   1                  1                 2

If we have 2.05 x 10^-4 moles of Fe2+

FeF2(s)  --> Fe2+(aq) +      2F- (aq)

                2.05 x 10^-4         2 x 2.05 x 10^-4  

2 x 2.05 X 10^-4 = 5.1 x 10^-4 moles

So if in the solution is measured 2.05 x 10^-4 mol/L of [Fe2+] we have 5.1 x 10^-4 mol/L of [F-]