How do I set this up? The recommended procedure for preparing a very dilute solu

Question

How do I set this up?

The recommended procedure for preparing a very dilute solution is not to weigh out a very small mass or measure a very small volume of stock solution. Instead, it is done by a series of dilutions. A sample of 0.8899 g of KMnO4 was dissolved in water and made up to the volume in a 500.0-mL volumetric flask. A 2.000-mL sample of this solution was transferred to a 1000-mL volumetric flask and diluted to the mark with water. Next, 10.00 mL of the diluted solution was transferred to a 250.0-mL flask and diluted to the mark with water. Calculate the concentration (in molarity) of the final solution. Enter your answer in scientific notation. times 10 M Calculate the mass of KMnO4, needed to directly prepare the final solution. Enter your answer in scientific notation. times 10 g

Explanation / Answer

Moles of KMnO4 in 500.0 mL flask = mass/molar mass of KMnO4

= 0.8899/158.034 = 0.00563107 mol


Moles of KMnO4 in 1000 mL flask = 2.000/500.0 x Moles of KMnO4 in 500.0 mL flask

= 2.000/500.0 x 0.00563107

= 2.25243 x 10^(-5) mol


Moles of KMnO4 in 250.0 mL flask = 10.00/1000 x Moles of KMnO4 in 1000 mL flask

= 10.00/1000 x 2.25243 x 10^(-5)

= 2.25243 x 10^(-7) mol


(a) Final concentration = moles/volume of KMnO4 in 250.0 mL flask

= 2.25243 x 10^(-7)/0.2500

= 9.010 x 10^(-7) M


(b) Mass of KMnO4 = Moles of KMnO4 in 250.0 mL flask x molar mass of KMnO4

= 2.25243 x 10^(-7) x 158.034

= 3.560 x 10^(-5) g

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