Chapter 3, Problem 3.111P

High-temperature superconducting oxides hold great promise in the utility, transportation, and computer industries.

(a) One superconductor is ${\text{La}}_{\text{2-}x}{\text{Sr}}_x{\text{CuO}}_{\text{4}}$. Calculate the molar masses of this oxide when $x=0,x=1,\text{ and }x=0.163$.

(b) Another common superconducting oxide is made by heating a mixture of barium carbonate, copper(II) oxide, and yttrium(III) oxide, followed by further heating in ${\text{O}}_{\text{2}}$ : $\begin{array}{l}{\text{4BaCO}}_3\left(s\right)+6\text{CuO}\left(s\right)+{\text{Y}}_2{\text{O}}_3\left(s\right)\to \\ 2{\text{YBa}}_{\text{2}}{\text{Cu}}_{\text{3}}{\text{O}}_{\text{6}\text{.5}}\left(s\right)+4{\text{CO}}_{\text{2}}\left(g\right)2{\text{YBa}}_2{\text{Cu}}_{\text{3}}{\text{O}}_{\text{6}\text{.5}}\left(s\right)+\frac{1}{2}{\text{O}}_2\left(g\right)\to \\ 2{\text{YBa}}_2{\text{Cu}}_3{\text{O}}_{\text{7}}\left(s\right)\end{array}$ When equal masses of the three reactants are heated, which reactant is limiting?

(c) After the product in part (b) is removed, what is the mass percent of each reactant in the remaining solid mixture?