# Superconductivity

Chemistry Level pending

Two identical samples of $$\ce{YBa2Cu3O7_y}$$ (YBCO) with an unknown value of $$y$$ were prepared. The first sample was dissolved in 5 mL of 1.0 M aqueous $$\ce{ HCl}$$, evolving $$\ce{O2}$$. After boiling to expel gases, cooling, and addition of 10 mL of 0.7 M $$\ce{KI}$$ solution under $$\ce{Ar}$$, titration with thiosulfate to the starch endpoint required 1.542 x 10-4 mol thiosulfate. The second sample of YBCO was added directly to 7 mL of a solution that was 1.0 M in $$\ce{KI }$$ and 0.7 M in $$\ce{HCl}$$ under $$\ce{Ar}$$; titration of this solution required 1.696 x 10-4 mol thiosulfate to reach the endpoint. Calculate the value of $$y$$ for these samples of YBCO.

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