High School

What mass of chromium (Cr) is contained in 35.8 g of \((NH_4)_2Cr_2O_7\)?

Answer :

M{(NH₄)₂Cr₂O₇}=2A(N)+8A(H)+2A(Cr)+7A(O)

M{(NH₄)₂Cr₂O₇}=252.065 g/mol

M(Cr)=51.996 g/mol

m{(NH₄)₂Cr₂O₇}/M{(NH₄)₂Cr₂O₇}=m(Cr)/2M(Cr)

m(Cr)=2M(Cr)m{(NH₄)₂Cr₂O₇}/M{(NH₄)₂Cr₂O₇}

m(Cr)=2*51.996*35.8/252.065=14.770 g

m(Cr)=14.770 g

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