When the high-temperature superconductor yttrium barium copper oxide (see Chapter 15 opening and Box 15-3) is heated under flowing H2, the solid remaining at 1 000C is a mixture of Y2O3, BaO, and Cu. The starting material has the formula YBa2Cu3O7 x, in which the oxygen stoichiometry varies between 7 and 6.5 (x 0 to 0.5).

(a) Thermogravimetric analysis. When 34.397 mg of YBa2Cu3O7 - x were subjected to this analysis, 31.661 mg of solid remained after heating to 1 000C. Find the value of x in YBa2Cu3O7 - x.
(b) Propagation of error. Suppose that the uncertainty in each mass in part (a) is ± 0.002 mg. Find the uncertainty in the value of x.

Transcribed Image Text:

1 000 C YBa Cu,O, (3.5 x)H2(g) FM 666.19-16.00x Y2Os) 2B3Cu(s)+ (3.5 x)HO(g)