In what substance is the mass fraction of oxygen greater than H₃SO₄ and H₃PO₄?

Given:
H2SO4
H3PO4

To find:
ω (O in H2SO4) -?
ω (O in H3PO4) -?

1) M (H2SO4) = Mr (H2SO4) = Ar (H) * N (H) + Ar (S) * N (S) + Ar (O) * N (O) = 1 * 2 + 32 * 1 + 16 * 4 = 98 g / mol;
2) ω (O in H2SO4) = N (O in H2SO4) * Ar (O) * 100% / Mr (H2SO4) = 4 * 16 * 100% / 98 = 65.31%;
3) M (H3PO4) = Mr (H3PO4) = Ar (H) * N (H) + Ar (P) * N (P) + Ar (O) * N (O) = 1 * 3 + 31 * 1 + 16 * 4 = 98 g / mol;
4) ω (O in H3PO4) = N (O in H3PO4) * Ar (O) * 100% / Mr (H3PO4) = 4 * 16 * 100% / 98 = 65.31%;
5) ω (O in H2SO4) = ω (O in H3PO4).

Answer: Mass fractions of O in H2SO4 and H3PO4 are equal.