Question

A 4.000 g sample of an unknown metal, M, was completely burned in excess O2 to yield 0.02225 mol of the metal oxide, M2O3. What is the metal

Answer 1

4X + 3O₂ = 2X₂O₃

n(X₂O₃)=0.02225 mol
m(X)=4.000 g
x - the molar mass of metal

m(X)/4x=n(X₂O₃)/2

x=m(X)/{2n(X₂O₃)}

x=4.000/{2*0.02225)=89.89 g/mol

X=Y (yttrium)