An aqueous solution of iron(II) iodide has a concentration of 0.215 molal. The percent by mass of iron(II) iodide in the solution is

6.24%

Explanation:

Molality by definition means a measurement of the number of moles of solute in solution with 1000 gm or 1Kg solvent. Notice the difference that Molarity is defined on the volume of solution and Molality on the mass of solvent.

So, An aqueous solution of iron(II) iodide has a concentration of 0.215 molal.

means 0.215 moles are present in 1 Kg of solvent.

The molar mass of Fe2I = 309.65 g / mole

mass of FeI2 = moles x molar mass

= 0.215 x 309.65

=66.57 gm

mass % of FeI2 = mass of FeI2 x 100 / total mass

= 66.57x 100 / (1000 +66.57)

= 6.24%