Li 1 y CoO 2 is an anode for lithium batteries Cobalt is present as a mixture of Co(III) and Co(II) Most preparations also contain inert lithium salts and moisture To find the stoichiometry, Co was measured by atomic absorption and its average oxidation state was measured by a potentiometric tritration For the titration, 25 00 mg of solid were dissolved under N 2 in 5 000 mL containing 0 100 0 M Fe 2 in 6 M H 2 S O 4 plus 6 M H 3 PO 4 to give a clear pink solution Co 3 Fe 2 CO 2 Fe 3 Unreacted Fe 2 required 3 228 mL of 0 015 93 M K 2 Cr 2 O 7 for complete titration (a) How many mmol of Co 3 are contained in 25 00 mg of the material (b) Atomic absorption found 56 4 wt Co in the solid What is the average oxidation state of Co (c) Find y in the formula Li 1 y CoO2 (d) What is the theoretical quotient wt Li wt Co in the solid The observed quotient, after washing away inert lithium salts, was 0 138 8 0 000 6 Is the observed quotient consistent with the average cobalt oxidation state

Question: Li 1 + y CoO 2 is an anode for lithium batteries. Cobalt is present as a mixture of Co(III) and Co(II). Most preparations also

Li_{1 + y}CoO₂is an anode for lithium batteries. Cobalt is present as a mixture of Co(III) and Co(II). Most preparations also contain inert lithium salts and moisture. To find the stoichiometry, Co was measured by atomic absorption and its average oxidation state was measured by a potentiometric tritration. For the titration, 25.00 mg of solid were dissolved under N₂ in 5.000 mL containing 0.100 0 M Fe²⁺ in 6 M H₂S_O4 plus 6 M H₃PO₄ to give a clear pink solution:

Co₃+ + Fe²⁺ → CO²⁺ + Fe³⁺

Unreacted Fe²⁺ required 3.228 mL of 0.015 93 M K₂Cr₂O₇ for complete titration.

(a) How many mmol of Co³+ are contained in 25.00 mg of the material?

(b) Atomic absorption found 56.4 wt% Co in the solid. What is the average oxidation state of Co?

(d) What is the theoretical quotient wt% Li/wt% Co in the solid? The observed quotient, after washing away inert lithium salts, was 0.138 8 ± 0.000 6. Is the observed quotient consistent with the average cobalt oxidation state?

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