A sample of an impure ore contains 42.7% Cr2O3 by mass. What is the mass percentage of chro- mium in the ore

29.21%

Explanation:

first of all we have to find the mass percentage of Cr in Cr2O3

molar mass of Cr2O3,

Molar Mass = 2 x Molar Mass(Cr) + 3 x Molar Mass(O)

= 2x52.0 + 3x16.0

= 104+48

= 152 g/mol

the Molar Mass of Cr2O3 = 152

we will calculate the mass of this element

mass of Cr = 2xMolarMass of (Cr)

= 104 g

Mass percentage of Cr = (104x100)/152

= 10400/152

= 68.42 %

therefore,

the fraction of Cr in ore is the fraction of Cr in Cr2O3 multi[plied by fraction of Cr2O3 in ore

42.7%

= 0.427

= 0.6842 * 0.427

= 0.292 1

when converted to %

= 29.21%

29.21 %

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