Determination of Manganase in an Ore using ICP. In the last sentence of procedur

Question

Determination of Manganase in an Ore using ICP.

In the last sentence of procedure, how do I prepare an appropriate dilution of the sample so that it will have a Mn concentration between 1 to 10mg/L. (Unknown contains between 25 and 45wt%Mn)

edure: 0.5 o16 Dissolve duplicate -0.1g samples (record to the nearest 0.0001 g) of an unknown in 3-6 mL of 4 M nitric acid (must be prepared by the student) on a hot plate in a hood. Heat the two samples. After they are warm, fdd30% H2O2 (hydrogen peroxide-be careful with this solution) one mL at a time to each sblution until the sample dissolves (this will probably only require one mL for each). Boil for a few minutes in the hood to remove nitric oxide - DO NOT BOIL OFF ALL OF THE LIQUID. Quantitatively transfer the two samples totwo 100 mL volumetric flasks. Use a solution containing 1 mL of concentrated HNOs per liter to ditfute your solutions. Prepare an appropriate dilution of your sample so that it will have a Mn concentration between 1 to 10 mgL-remember, the unknown contains between 25 and 45 wt% Mn. o0,9

Explanation / Answer

Dilute the solution any value between 250 to 45 time to get the required concentration of Mn, 1 to 10 mg/L.

--calculations--

The sample weight = 0.1 g, it was made up to 100 mL in a standard flask.

The sample contains Mn between 25 and 45 wt%

which means that 0.1 g of sample contains = 0.1 g x 25 / 100 = 0.025   to 0.1 g x 45/100 = 0.045 g of Mn ions

So in 100 mL solution you have a Mn concentration from 0.025 g (25 mg) to 0.045 g (45 mg).

i.e. 25-45 mg/ 100 mL = 250 - 450 mg / L, so in order to bring down the concentration between 1-10 mg/L you have to dilute sample between 250 times to 45 times (250 /250 = 1 to 450/45 = 10),

i.e. if you dilute 250 times, i.e. take 1 mL of the solution from the standard flask and make to volume to 250 mL, the concentration of Mn will be 250 / 250 mg to 450 / 250 = 1 to 1.8 mg/L.

If you dilute 45 times, i.e. 1 mL of the solution to 45 mL (or 5.55 mL solution make up in a 250 mL flask) the concentration of Mn will be 5.5 - 10 mg/L.

So you can dilute the solution any value between 250 to 45 to get the required concentration of 1 to 10 mg/L

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