in the laboritory a chemist prepares a stock solution of ammonium sulfate by pla

Question

in the laboritory a chemist prepares a stock solution of ammonium sulfate by placing 228.20g of the solid into a 500.00mL volumetric flask and filling it to the mark with distilled water.

a)Determine the concentration(molarity) of the stock solution

b)125.00mL of the original stock solution in (a) is removed and placed in a second 500.00 mL volumetric flask and diluted to mark with water. Determine the Molarity of the dilute solution.

c)What volume of the original stock solution in (a) should the chemist remove to make 250.00mL of a 0.20M ammonium sulfate solution?

Explanation / Answer

a) Molar mass of ammonium sulfate = 132.14 gm/mol

Number of moles of ammonium sulfate = mass/molar mass = 228.20/132.14 = 1.726 moles

Molarity = number of moles of solute/volume of solution in L

=> 1.726/(0.5)

=> 3.453 M

b) M1V1 = M2V2

(3.453)(125) = (M2)(500)

M2 = 0.8634M

c)

M1V1 = M2V2

(3.453)(V1) = (250)(0.20)

V1 = 14.480 mL

Volume of original stock solution removed = 500 - 14.480 = 485.51 mL

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