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?

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-]

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