## Chemistry and Chemical Reactivity (9th Edition)

Published by Cengage Learning

# Chapter 4 Stoichiometry: Quantitative Information about Chemical Reactions - Study Questions - Page 179k: 124

#### Answer

$x=0.268$

#### Work Step by Step

Final titration: $0.1542\ mmol\ thiosulfate\rightarrow 0.0771\ mmol\ I_3^-$ Potassium iodate addition: $10\ mL\times 0.70\ M=7.0\ mmol$, from stoichiometry, $1.4\ mmol\ I_3^-$ would be formed, so iodate is in excess. Number of moles of $Cu^{2+}: 0.1542\ mmol$ Number of moles of the compound: $0.05214\ mmol$ Molar mass of the compound: $34.02\ mg/0.05214\ mmol=661.9\ g/mol$ $661.9=88.906+2\times 137.327+3\times 63.546+(7-x)\times 15.9994$ $x=0.268$

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