What mass of chromium (cr) is contained in 35.8 g of (nh4) 2cr2o7?

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