Electrochemistry Calculations Using the Nernst Equation

The Nernst equation is used to calculate the voltage of an electrochemical cell or to find the concentration of one of the components of the cell. The Nernst Equation The Nernst equation relates the equilibrium cell potential (also called the Nernst potential) to its concentration gradient across a membrane. An electric potential will form if there is a concentration gradient for the ion across the membrane and if selective ions channels exist so that the ion can cross the membrane. The relation is affected by temperature and whether the membrane is more permeable to one ion over others. The equation may be written: Ecell E0cell - (RT/nF)lnQ Ecell cell potential under nonstandard conditions (V)E0cell cell potential under standard conditionsR gas constant, which is 8.31 (volt-coulomb)/(mol-K)T temperature (K)n number of moles of electrons exchanged in the electrochemical reaction (mol)F Faradays constant, 96500 coulombs/molQ reaction quotient, which is the equilibrium expression with initial concentrations rather than equilibrium concentrations Sometimes it is helpful to express the Nernst equation differently: Ecell E0cell - (2.303*RT/nF)logQ at 298K, Ecell E0cell - (0.0591 V/n)log Q Nernst Equation Example A zinc electrode is submerged in an acidic 0.80 M Zn2 solution which is connected by a salt bridge to a 1.30 M Ag solution containing a silver electrode. Determine the initial voltage of the cell at 298K. Unless youve done some serious memorizing, youll need to consult the standard reduction potential table, which will give you the following information: E0red: Zn2aq 2e- → Zns -0.76 V E0red: Agaq e- → Ags 0.80 V Ecell E0cell - (0.0591 V/n)log Q Q [Zn2]/[Ag]2 The reaction proceeds spontaneously so E0 is positive. The only way for that to occur is if Zn is oxidized (0.76 V) and silver is reduced (0.80 V). Once you realize that, you can write the balanced chemical equation for the cell reaction and can calculate E0: Zns → Zn2aq 2e- and E0ox 0.76 V 2Agaq 2e- → 2Ags and E0red 0.80 V which are added together to yield: Zns 2Agaq → Zn2a 2Ags with E0 1.56 V Now, applying the Nernst equation: Q (0.80)/(1.30)2 Q (0.80)/(1.69) Q 0.47 E 1.56 V - (0.0591 / 2)log(0.47) E 1.57 V

Econ - 1874 Words

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Debut Albums and Ms. Levine English free essay sample

After you left me all I was left with Is shock and great grief I lost you, best friend. I lust seem to cant take in the fact that you left me all alone In this cold hard world and you are not by my side anymore. After you made become a walking zombie. I was too sad and depressed to eat or sleep; or even function right. You were my other half, my twin, but most importantly we were more then sisters.Our friendship could never ampere to anything, we were thicker then a peanut butter and Jelly sandwich. We did EVERYTHING together. The love I have for you no one could ever replace That. I would tell you that I love you more then Sponge loves Jelly fishing. Sandy loves karate. Mr.. Grabs loves money. sluggard loves his clarinet I need her Like Plankton needs the Crabby Patty Secret Formula. We will write a custom essay sample on Debut Albums and Ms. Levine English or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page I miss you so much I need you back in my life. I want to tell you that our memories will never fade; it will always be locked up tight n my heart and I will forever cherish those memories. She always been there for me, because you were my best friend, and I was always there for her until the very end. Even though that I will miss you, and Ill think about you everyday youll always be my best friend, and thats all I have to say. I hope youre in a better and happier place and I hope youre always by my side guiding me through hard times because even thought you not with me youll always live inside of me. [pica Always and Forever!

Debates Abraham Lincoln and Slavery Extension Issue free essay sample

Lincoln and Douglas debated the slavery extension issue in 1 858, therefore, they were addressing the problem that had divided the nation into two hostile camps. The issue that threatened the continued existence of the nation. Lincoln spoke out against the union. Say that the country wont survive long if it is split. Douglas took this as an opportunity, and referred to Lincoln as a radical. Lincoln then challenged Douglas to a series of debates, and the two eventually agreed to have seven debates in the state of Illinois.The debates, each three hours long, were convened in Ottawa held August 1 , Freeport held August 27, Joneses held September 15, Charleston held September 18, Eagleburger held October 7, Quince held October 13, and Alton held October 15. Douglas repeatedly tried to brand Lincoln as a dangerous radical who stood for racial equality and disruption of the Union. Lincoln emphasized the moral iniquity of slavery and attacked popular sovereignty for the blood it had spilled in Kansas. We will write a custom essay sample on Debates: Abraham Lincoln and Slavery Extension Issue or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page In the first debate in Ottawa, Douglas accused Lincoln of trying to get rid of the Whig and democratic party.He also said that Lincoln was taking the side f the common enemy in the Mexican War. He even decided to say that Lincoln wanted to make Illinois a free negro colony. Which then was not a normal view. At the debate in Freeport Lincoln challenged Douglas to reconcile popular sovereignty with the Dried Scott decision. Douglas replied that settlers could make the decision by not establishing the local police regulations that protected a masters property. Without that protection, no one with slaves would move into that territory.In the third debate, in Joneses, Illinois, Douglas tried to make Lincoln me unreliable. Saying that Locoing said something new, or took a new stance on an issue in the different parts of Illinois. He again repeated that Lincoln stood for racial equality. Lincoln denied all of the accusations except for the racial equality. In the fourth debate, in Charleston, Illinois, Lincoln accused that Douglas was plotting to create a constitution for Kansas allowing it to be voted upon by the people of Kansas. Lincoln gave a detailed history of the Kansas Nebraska Act and explained a conspiracy to nationalize slavery. Douglas ended the conspiracy, and restated again, that Lincoln wanted equality of the races. In the fifth debate, in Eagleburger, Illinois, Douglas explained how he opposed the Locomotion Constitution as well as an compromise on the issue. He made a statement on how the Declaration of Independence was written by white men, and was only mean to apply to white men. Lincoln stated how he believed that the Declaration of Independence was meant to apply to all men. In the sixth debate, in Quince, Illinois, Lincoln again denied that he said different things at different debates.He emphasized how slavery was morally wrong, and promised that Republicans would attack slavery where the constitution allowed them to. Douglas refused to argue whether or not slavery was right or wrong, he insisted that each local area should have the right to decide for themselves. In the seventh debate, in Alton, Illinois, Lincoln stated that the Kansas Nebraska Act repealed Henry Clays Missouri Compromise. Lincoln used Clays statements that slavery was evil and Lincoln charged that by excluding the other races from the Declaration of Independence Douglas euthanized ND tool away from their rights to strive and be free.