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The concentration of a solution can be expressed in terms of its molarity (M). A solution with a molarity of one has a concentration of one mole of the solute in every one liter of the solution.
Here we have a solution that contains 200 grams of iron (II) chloride in 450 mL of the solution. I have taken the iron (II) chloride to be anhydrous in nature. This has a molecular mass of 126.751 g/mole.
200 g of the compound constitutes 200/126.751 = 1.577 moles.
1.577 moles dissolved in 450 mL of the solution gives a molarity of 1.577/0.450 = 3.5
The required concentration of the 450 mL solution that contains 200 g of iron (II) chloride is 3.5 M.
Moles = mass of solute/ gram molecular mass. Solute is the 'stuff being disolved. Solution is a homogeneous mixture of a solute in a solvent
. moles of solute
Molarity is defined as: ____________________
. liters of solution
In this problem (assuming the values given are both to 3 significant figures)
. 200g / 127 g / mol 1.57 mol
Molarity = ___________________ = ________ = 3.50 M FeCl2
. 450mL * 1 L/1000ml 0.450 L
I ALWAYS recommended to my students that they attach the chemical formula (eg: FeCl2) as a subscript behind the unit of meaure symbol (eg: M).
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