Question

part 1 (3 points)
chromium is most commonly mined in the form of chromite, which has the chemical formula fecr₂o₄. calculate the percent by mass of each element in chromite, and give your answers to four significant digits.
%fe =
%cr =
%o =

part 2 (1 point)
using the information from part 1, how much cr metal could be extracted from 177.1 g of chromite? round your answer to four significant digits.

choose one:
41.14g
44.19g
82.28g
50.63g

Explanation:

Step1: Calculate molar mass of FeCr₂O₄

The molar mass of Fe ($M_{Fe}=55.85\ g/mol$), Cr ($M_{Cr}=52.00\ g/mol$), O ($M_{O}=16.00\ g/mol$).
$M_{FeCr_{2}O_{4}}=55.85 + 2\times52.00+4\times16.00=55.85 + 104.00+64.00 = 223.85\ g/mol$

Step2: Calculate %Fe

$\%Fe=\frac{55.85}{223.85}\times100\% \approx 24.95\%$

Step3: Calculate %Cr

$\%Cr=\frac{2\times52.00}{223.85}\times100\%=\frac{104.00}{223.85}\times100\%\approx46.46\%$

Step4: Calculate %O

$\%O=\frac{4\times16.00}{223.85}\times100\%=\frac{64.00}{223.85}\times100\%\approx28.59\%$

Step5: Calculate mass of Cr in 177.1 g of chromite (for Part 2)

Mass of Cr = mass of chromite $\times$ %Cr/100
Mass of Cr = $177.1\times\frac{46.46}{100}\approx82.28\ g$

Answer:

%Fe = 24.95%
%Cr = 46.46%
%O = 28.59%
Part 2: C. 82.28 g