Question

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.

Answer 1

 

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%