A) Answer is: 51.48% V and 48.52% O.
Ar(V) = 50.94; atomic weight of vanadium.
Ar(O) = 16; atomic weight of oxygen.
Ar(VO₃) = 50.94 + 3 · 16.
Ar(VO₃) = 98.94; molecular weight of vanadium (VI) oxide.
ω(V) = Ar(V) ÷ Ar(VO₃) · 100%.
ω(V) = 51.48%; the percent composition of vanadium.
ω(O) = 100% - 51.48%.
ω(O) = 48.52%; the percent composition of oxygen.
B) Answer is: 67.80% V and 32.20% O.
Ar(V) = 50.94; atomic weight of vanadium.
Ar(O) = 16; atomic weight of oxygen.
Ar(V₂O₅) = 2 · 50.94 + 5 · 16.
Ar(V₂O₅) = 149.88; molecular weight of vanadium (V) oxide.
ω(V) = 2 · Ar(V) ÷ Ar(V₂O₅) · 100%.
ω(V) = 67.80%; the percent composition of vanadium.
ω(O) = 100% - 67.80%.
ω(O) = 32.20%; the percent composition of oxygen.
