Chem 102 1st Edition Lecture 15 Outline of Last Lecture I. Gibb’s Free EnergyII. Free Energy and TemperatureIII. Free Energy and The Equilibrium Outline of Current LectureI. Oxidation- Reduction ReactionII. Voltaic CellsIII. Cell EMFIV. Spontaneity of Redox ReactionsCurrent LectureI. Oxidation-Reduction Reactions-Law of Conservation of Mass: the amount of each element present at the beginning ofthe reaction must be present at the end. -Conservation of Change: Electrons are not lost in a chemical reaction. -In complicated redox reactions, we have to carefully look at the transfer of electrons. -Half Reactions- A convenient way of separation oxidation and reduction reactions. Oxidation electrons are products and reduction electrons are reagents. -Balancing these equations: First write down the 2 half-reactions, than balance them both. Next, multiply each half reaction to make the number of electrons equal. Add the reactions and simplify. -We use OH- and H2O rather than H+ and H2O, OH- is added to neutralize the H+ used.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. Voltaic Cells- The energy released in a spontaneous redox reaction is used to perform electrical work. Voltaic or galvanic cells are devices in which electron transfer occurs via an external circuit. -Voltaic cells are spontaneous. They consist of anodes, cathodes, and salt bridges where cations move and flow from anode to cathode. The anode is negative and the cathode is positive, electrons cannot flow through the solution, they have to flow through an external wire. III. Cell EMF-The flow of electrons from anode to cathode is spontaneous. They flow because the cathode has a lower electrical potential energy than the anode. -Potential difference- The difference in electrical potential, measured in volts. 1V= 1J/1C-EMF= Electromotive Force, the force required to push electrons through the external circuit. Cell potential: Ecell is the EMF of a cell. Standard conditions are 1M and 25 degrees Celsius. -Standard Reduction Potentials- Measured relative to the standard hydrogen electrode. The SHE is the cathode and can be calculated E(cathode) – E(anode). E greater than 0 are spontaneous reductions, E less than 0 spontaneous oxidations. IV. Spontaneity of Redox Reactions- DG = -nFEG being free energy, n is the number of moles, E is the EMF cell, and F is
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