A compound consisting of yttrium(III) ions, barium(II) ions, both copper(II) and copper(III) ions, and oxide ions is a superconducting material at low temperatures. It has the formula YBa₂Cu₃O_7−x where x is a variable between 1 and 0. To find out the value of x, you dissolve 34.02 mg of the compound in 5 mL of 1.0 M HCl. Bubbles of oxygen gas (O₂) are observed as the following reaction occurs:

You then boil the solution, cool it, and add 10 mL of 0.70 M KI under argon. The following reaction occurs: 

When this reaction is complete, a titration of the resulting solution with sodium thiosulfate requires 1.542 × 10⁻⁴ mol S₂O₃²⁻(aq).

What is the value of x in YBa₂Cu₃O_7−x?

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YBa₂Cu3O7-x(s) + 13 H+ (aq) - Y³+(aq) + 2 Ba²+ (aq) + 3 Cu²+(aq) + 1/4(1 2x) O₂(g) + 13/2 H₂O(l)