Question

In the laboratory you dissolve 12.2 g of iron(II) iodide in a volumetric flask and add water to a total volume of 500 mL.

What is the molarity of the solution?
M.

What is the concentration of the iron(II) cation?
M.

What is the concentration of the iodide anion?
M.

Answer 1

a.) 0.0788 M

b.) 0.0788 M

c.) 0.156 M

Step-by-step explanation:

To find the molarity of the solution, you need to (1) convert grams FeI₂ to moles FeI₂ (via the molar mass from periodic table) and then (2) calculate the molarity (via the molarity equation using the moles and volume). To find the concentration of each ion, you need to multiply the compound's molarity by the amount of each ion in the molecule.

(Step 1)

Molar Mass (FeI₂): 55.845 g/mol + 2(126.90 g/mol)

Molar Mass (FeI₂): 309.645 g/mol

12.2 g FeI₂ 1 mole
------------------ x --------------------- = 0.0394 mole FeI₂
309.645 g

(Step 2)

500 mL / 1,000 = 0.5 L

Molarity (M) = moles / volume (L)

Molarity = 0.0394 mole / 0.5 L

Molarity = 0.0788 M

(Step 3)

FeI₂ = 1 iron cation and 2 iodide anions

Iron (II) Cation: 1 x 0.0788 M = 0.0788 M

Iodide Anion: 2 x 0.0788 M = 0.156 M