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1716f_Electrochem_Practice_problems

1716f_Electrochem_Practice_problems - Raffles Raffles...

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Practice Problem 1: 35 th Olympiad Sealed type Ni – Cd batteries (“Nicad”) are widely used in portable devices such as cordless power tools, cellular telephones, camcorders, portable computers, etc. Ni –Cd batteries are cost-effective and have high cycle lives and excellent low or high temperature performance. They require no maintenance and can be recharged up to 2000 times. A typical sealed type Ni – Cd cell consists of the following two half-cells: Cd(OH) 2 (s) + 2e Cd (s) + 2OH - E 0 1 = -0.809V 2NiO(OH) (s) + 2H 2 O + 2e 2Ni(OH) 2 (s) + 2OH - E 0 2 = - 0.490 V where E 0 1 , E 0 2 are standard reduction potentials at 25 o C. Questions : 1. Which reaction occurs at the cathode? Give the corresponding Nernst equation for the potential. 2. Which reaction occurs at the anode? Give the corresponding Nernst equation for the potential. 3. Write a balanced equation that shows the reaction that occurs spontaneously as the cell discharges. 4. Calculate the electromotive force E of the cell at 25 o C. 5. What is the mass of Cd contained in a cellular telephone Ni – Cd battery of a nominal capacity of 700 mAh ? Practice Problem 2: Raffles Junior College Raffles Junior College Raffles Junior College Chemistry Olympiad Chemistry Olympiad
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