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What mass of chromium is present in 234 grams of an ore of chromium that is 55.0% iron(ii) dichromate, FeCr2O7, and 45.0% impurities by mass

Accepted Answer

Here's how to calculate the mass of chromium:
1. Calculate the mass of FeCr2O7:

Mass of FeCr2O7 = 234 g ore
0.550 = 128.7 g FeCr2O7
2. Calculate the moles of FeCr2O7:

Molar mass of FeCr2O7 = 55.845 g/mol (Fe) + 2
52.00 g/mol (Cr) + 7
16.00 g/mol (O) = 271.845 g/mol

Moles of FeCr2O7 = 128.7 g / 271.845 g/mol = 0.473 mol FeCr2O7
3. Calculate the moles of chromium:

There are 2 moles of Cr in 1 mole of FeCr2O7

Moles of Cr = 0.473 mol FeCr2O7
(2 mol Cr / 1 mol FeCr2O7) = 0.946 mol Cr
4. Calculate the mass of chromium:

Mass of Cr = 0.946 mol
52.00 g/mol = 49.2 g Cr
Therefore, there are 49.2 grams of chromium present in the ore.

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