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Ch.19 - Electrochemistry
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Not the one you use?Change textbook
All textbooksTro 4th EditionCh.19 - ElectrochemistryProblem 83
Chapter 19, Problem 83

Determine the optimum mass ratio of Zn to MnO2 in an alkaline battery.

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1
Identify the chemical reactions involved in the operation of an alkaline battery, focusing on the reactions of zinc (Zn) and manganese dioxide (MnO2).
Write the balanced chemical equations for the oxidation of Zn and the reduction of MnO2 in the battery.
Calculate the molar masses of Zn and MnO2 using the periodic table to understand how much each substance weighs per mole.
Use stoichiometry from the balanced equations to determine the mole ratio of Zn to MnO2 required for the reactions to proceed completely without any excess reactant.
Convert the mole ratio into a mass ratio by multiplying the mole ratio by the molar masses of Zn and MnO2, respectively. This will give you the optimum mass ratio of Zn to MnO2 for the battery.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions. It involves using balanced chemical equations to determine the proportions of elements or compounds needed for a reaction. In the context of the Zn and MnO2 ratio, stoichiometry helps identify the optimal mass ratio based on their molar relationships in the battery's electrochemical reactions.
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Electrochemistry

Electrochemistry is the branch of chemistry that deals with the relationship between electrical energy and chemical changes. In alkaline batteries, the redox reactions between zinc and manganese dioxide generate electrical energy. Understanding the electrochemical processes is crucial for determining how the mass ratio affects the battery's efficiency and performance.
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Battery Chemistry

Battery chemistry refers to the study of the chemical reactions that occur within a battery to store and release energy. In alkaline batteries, zinc acts as the anode and MnO2 as the cathode. The optimum mass ratio of these materials is essential for maximizing energy output and ensuring the battery operates effectively over its lifespan.
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A Cu/Cu2+ concentration cell has a voltage of 0.22 V at 25 °C. The concentration of Cu2+ in one of the half-cells is 1.5×10–3 M. What is the concentration of Cu2+ in the other half-cell? (Assume the concentration in the unknown cell is the lower of the two concentrations.)

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Consider the concentration cell: b. Indicate the direction of electron flow.

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