Chem 1465 1st Edition Lecture 18Outline of Last Lecture 1. Redox reactions A. TermsB. Balancing a redox equation Outline of Current Lecture1. Cell notation2. Cell potential A. Galvanic cellsB. Measuring cell potentialC. Standard reduction potentials D. Nonstandard conditions3. Cell potential and equilibrium Current Lecture1. Cell notation- General notation:Anode │ electrolyte of anode ││ cathode │ electrolyte of cathode- Components of anode go on the left and the components of the cathode go on the right (the spectator ions are left out)- Vertical lines spate phase boundaries and commas spate components in the same phase- The electrodes are contained on the outsides- Double vertical lines separate the half cells and represent the salt bridgeThese 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.2. Cell potentialA. Galvanic cells have potential: for the cells there are 2 components, with one component “pulling” electrons through the wire- Ecell = the cell potential, the “pull”- Units are emf or voltage- Spontaneous when Ecell is positive B. Measuring cell potential- There are no absolute values for potentials, therefore we must compare relative to each other- SHE- standard hydrogen electrode where 2H+ + 2e- → H2 and Ecell = 0 volts C. Standard reduction potentials- Convention: it is common to write all half reactions as reductions - Therefore- only reactants are oxidizing agents and only the products are reducing agents- The value of Eᵒ give us important information: the higher or larger the value of Eᵒ, the reaction goings forward; the smaller the value of Eᵒ, the reaction goes in reverse- Eᵒhalf cell is an intensive property- it does not depend on the amount- To calculate cell potential: Eᵒcell =Eᵒreduced - Eᵒoxidized D. Nonstandard conditions- The standard state is 1 molar and 1 atm; when not in standard conditions- use the Nernst equation - Nernst equation: Ecell = Eᵒcell – (RT/ nF) x (ln(q))Where q is quotient ([product] / [reactants]) F = 96,500 and R = 8.314 n = number of moles of electrons transferred 3. Cell potential and equilibrium - Since cell potential informs us on spontaneity it must be related to ΔGᵒ and K- For spontaneous reactions: ΔGᵒ is negativeK > 1Ecell is positive - For non-spontaneous reactions:ΔGᵒ is positiveK < 1Ecell is negative - How to calculate ΔGᵒ : ΔGᵒ = -nFEᵒcell Where n is the moles of electrons transferred and F =
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