chem module 14
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CHEM 1212 Module 14 Reading Guide
The Nernst Equation
In ____________cells, chemical energy is converted into electrical energy, which can do work. If E° > 0, the cell reaction is ____________under standard conditions. When the conditions are not standard, then the ____________equation is used to determine the cell potential (E). If E > 0, the reaction spontaneously proceeds in the ____________direction under those nonstandard conditions.
The value of n is the number of moles of ____________transferred in the balanced net ionic equation for the cell.
In a cell containing reactants at concentrations lower than 1.0 M, the reaction should proceed to a lesser degree, in which case E < E°. If the concentrations of solutes are higher than 1.0 M, then E > E°.
Practice Problems
What is the cell potential for the following reaction at room temperature?
Al(s)│Al3+(aq,0.15M)║Cu2+(aq,0.025M)│Cu(s)
Concentration cells
Because concentration affects potential, it is possible to make a cell in which both half-cells are identical except for the concentration of the ions. If both cells have identical concentrations of ions, the potential is 0 V, because the cell is at ____________. Reactions in concentration cells move spontaneously in the direction that brings the cell closer to equilibrium. To get a positive cell potential (spontaneous process) the reaction quotient Q must be less than ____. The magnitude of the difference in concentration between the half-cells is directly related to the magnitude of the cell potential. Typically, the voltages produced by concentration cells are much ____________than the voltages produced by other cells.
Practice Problems
What is the cell potential of the concentration cell described by
Zn(s)│Zn2+(aq, 0.10M)║Zn2+(aq, 0.50M)│Zn(s)
Redox reactions in use
The reactions of some voltaic cells are readily reversible, making it possible to recharge them by applying an outside source of electricity. A ____________is an electrochemical cell or series of cells that produces an electric current. Primary batteries are single-use batteries because they cannot be recharged. Secondary batteries are ____________. A _______cell is a sealed voltaic cell containing the mobile ions in a paste or gel form rather than an aqueous solution.
A ____________is a device that converts chemical energy into electrical energy that requires a continuous source of fuel.
Corrosion is the ____________of a metal object in soil or water that is accelerated by the unintentional formation of a voltaic cell. One way to prevent corrosion is to use a ____________ anode, made of a more active metal that is deliberately oxidized to protect the metal structure.
Electrolysis
Electrolysis causes a ____________chemical reaction to occur via an applied electrical potential. Electrolysis reactions require ions capable of movement and an external electrical current of sufficient ____________to cause the desired reaction to occur. Overpotential is the difference between the theoretical cell voltage and the ____________voltage that is necessary to cause electrolysis.
The amount of product produced by an electrolytic cell can be calculated from the quantity of ____________that passes through the cell, combined with the stoichiometry of the redox process.
If a specific amount of product is needed, the amount of current for a specific ____________can be calculated. Electrical current is measured in ____________, A, which are defined as the amount of electrical charge in coulombs that passes a point in one ____________.
Practice Problems
Calculate the mass of mercury deposited by a 10.0 A current passing for 3.00 h through Hg2(NO3)2(aq).
Text segments from OpenStax, Chemistry. OpenStax CNX. Sep 15, 2020 http://cnx.org/contents/[email protected].; White, J. et al. Interactive General Chemistry. MacMillan, NY. 2019.; Chemistry LibreTexts, Libretexts, [online] Available from: https://chem.libretexts.org/Courses/Heartland_Community_College/HCC:_Chem_161/5:_Thermochemistry/5.7:_Enthalpy_of_Formation. Reading guide style Adapted from "Ionic equations Study Guide" by Montgomery College is licensed under CC BY 4.0 Document not to be reposted on the internet without express permission.
