Answer to Question #344402 in General Chemistry for Nina

Question

Chemist to determine copper concentration in rock sample. Knowing copper undergoes redox reactions, they chose to use iodometric titration for analysis. Unknown sample weighing 1.5098g was acidified with 3.0M H2SO4 to dissolve copper compounds and diluted with 30mL distilled water. This was followed by addition of excess KI producing I2 and CuI precipitate from Cu2+(Reaction 1). Then, liberated I2 reacted with excess KI forming triiodide anion(Reaction 2), which was titrated with Na2S2O3 titrant(Reaction 3). This entire solution required 17.60 mL of titrant to reach starch end point.

MW: Cu (63.546)

a. Write balanced chemical equation for Reactions 1-3

b. Write mole ratio between Cu2+ and S2O32–

Prior to titration of sample, titrant was standardized by taking 50.0 mL of 6.7863x10-3M standard KIO3 solution, acidifying, and adding KI crystals. Titration of this solution required 9.80mL to reach starch endpoint.

c. Write concentration of S2O32– titrant in M

d. Write copper content of rock sample in %w/w

Answer 1

Such ineradicable task...