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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