## Chemistry and Chemical Reactivity (9th Edition)

$1240\ kg\ Cr_2O_3$
Atomic weights (g/mol): $Cr: 51.996,\ O: 15.999$ Molar mass: $151.99\ g/mol$ Mass fraction of Cr: $2\times51.996/151.99\times100\%=68.42\%$ For 850 kg of Cr: $850\ kg\ Cr\div(68.42 \ kg\ Cr/100\ kg\ Cr_2O_3)=1240\ kg\ Cr_2O_3$