In 1987 the first substance to act as a superconductor at a temperature above that of liquid nitrogen (77 k) was discovered. the approximate formula of this substance is yba2cu3o7. calculate the percent composition by mass of this material.

The molar mass of the elements are:

Yttrium (Y) = 88.91 g / mol

Barium (Ba) = 137.33 g / mol

Copper (Cu) = 63.55 g / mol

Oxygen (O) = 16 g / mol

Calculating for the molar mass of YBa2Cu3O7:

YBa2Cu3O7 = 88.91 + 2 (137.33) + 3 (63.55) + 7 (16) = 666.22 g / mol

The masses of the elements in 1 mole of YBa2Cu3O7 are:

Yttrium (Y) = 88.91 g / mol (1 mole) = 88.91 g

Barium (Ba) = 137.33 g / mol (2 mole) = 274.66 g

Copper (Cu) = 63.55 g / mol (3 mole) = 190.65 g

Oxygen (O) = 16 g / mol (7 mole) = 112 g

We now calculate for the percent composition by mass of each element:

% Y = 88.91 g / 666.22 g = 13.35%

% Ba = 274.66 g / 666.22 g = 41.23%

%Cu = 190.65 g / 666.22 g = 28.62%

%O = 112 g / 666.22 g = 16.81%