Find the concentration of iron(III) ions and nitrate ions in the solution.40.4 g of Fe(NO3)3. 9H2O is dissolved in sufficient water to make up one litre of solution.
40.4 g of Fe(NO3)3.9H2O is dissolved in a sufficient volume of water to create one liter of the solution. Each unit of Fe(NO3)3.9H2O provides 3 nitrate ions and one iron ion.
The molar mass of Fe(NO3)3.9H2O is 403.99
40.4 g of Fe(NO3)3.9H2O is approximately equivalent to 40.4/404.4 = 0.1 moles
As each unit of the hydrated iron nitrate contributes one unit of iron(3) ions, the concentration of iron(3) ions in the solution is 0.1 moles/liter.
As each unit of the hydrated iron nitrate contributes 3 units of nitrate ions, the concentration of nitrate ions if 0.3 moles/liter.