Is sulfur trioxide a homogeneous or heterogeneous mixture?

A mixture is the matter which composed of atleast two compounds or solute which comprises to produce either homogenous or hetrogenous mixture. Homogenous mixture is the mixture contains two or any number of compounds in similar ratio whereas hetrogenous mixture is the mixture contains number of compounds but their ratio is not similar.

Sulfur trioxide is a compound not any type of mixture. Sulfur trioxide is composed of sulfur atom along with three oxygen. Its hybridisation is sp^2 and having planar geometry.  

Thus, Sulfur trioxide is a compound not any type of mixture

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally