Answer
a) $2\ Cr + 3/2\ O_2\rightarrow Cr_2O_3$
b) $0.256\ g\ Cr_2O_3$
c)$0.081\ g\ O_2$
Work Step by Step
a) $2\ Cr + 3/2\ O_2\rightarrow Cr_2O_3$
b) Number of moles of metal:
$0.175\ g\div 51.996\ g/mol=0.00337\ mol$
From stoichiometry:
$0.00337\ mol\times 1_{Cr_2O_3}/2_{Cr}\times 151.99\ g/mol\ Cr_2O_3=0.256\ g\ Cr_2O_3$
c)From stoichiometry:
$0.00337\ mol\times 1.5_{O_2}/2_{Cr}\times 32.00\ g/mol\ O_2=0.081\ g\ O_2$
