Calculate the volume in liters of a ×4.3910−5/moll mercury(ii) iodide solution that contains 500.mg of mercury(ii) iodide hgi2 . round your answer to 3 significant digits.

The molarity of the solution is 4.39 x 10⁻⁵ mol/L
molarity is the number of moles of solute in 1 L of solution 
in this instance there are 4.39 x 10⁻⁵ mol of HgI₂ in 1 L solution 
the mass of HgI₂ in 1 L - 4.39 x 10⁻⁵ mol x 454.4 g/mol = 19.9 mg
if 19.9 mg are in 1 L 
then 500.0 mg are in - 500.0 mg / 19.9 mg/L = 25.1 L
therefore volume is 25.1 L

Yes she is correct. the answer is completely correct