CHEM10006 Lecture Notes - Lecture 31: Covalent Bond, Lone Pair, Nernst Equation

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magentamuskrat643

10 Aug 2018

School

University of Melbourne

Department

Chemistry

Course

CHEM10006

Professor

Frances Separovic

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Document Summary

The ne(cid:396)(cid:374)st e(cid:395)uatio(cid:374) allows us to calculate the pote(cid:374)tial at i(cid:374)te(cid:396)(cid:373)ediate ph"s. Standard reduction potentials depend on ph, and are based on unit concentrations. As ph = - log[h+], ecell = eo - 0. 0591 ph, which will graph to a straight line. Plot of e vs ph for the reduction of o2 and h2o. The stability field of water is the range of values of potential and ph for which water is thermodynamically stable towards both oxidation and reduction. Species with a potential more positive than the top line will release o2 from water. Species with a potential more negative than the bottom line will release h2 from water. Lines mark places where two species exist in equilibrium. Pure redox reactions are horizontal lines - these reactions are not ph-dependent. Pure acid-base reactions are vertical lines - these do not depend on potential. Reactions that are both acid-base and redox have a slope of -0. 0592 v/ph.

Related Questions

. Consider an electrochemical cell for the 2-electron conversion of CO2 to formate (HCOOâ ). Assume that the anode in this cell oxidizes water to O2 and runs at the standard redox potential for this reaction: ! ! O! + 2H! + 2 eâ â H!O ï¿½! Â° = 1.23 V vs. SHE (1) The standard redox potential for CO2 reduction to formate is: CO! + H!O + 2 eâ â HCOO! + OH! ï¿½! Â° = â0.23 V vs. SHE (2) However, an electrochemical cell cannot run at this potential because one can only dissolve 0.030M CO2 in water at STP. a. Assuming that a cell is constructed that contains CO2 saturated water and 0.010M formate at pH = 8, what is the minimum potential that will need to be applied to this cell to cause it to produce formate and oxygen at one atmosphere? b. If one mole the electrosynthesized formate is then ignited under standard conditions, what is the value of âHÂ° of combustion, given that the âSÂ° for this reaction is +52.23 J/moleK? c. In addition to formic acid, CO2 can be reduced to formaldehyde (H2CO), methanol and methane. Write out balanced half reactions to determine the number of electrons each transformation involves.