7._Chapter_21_electro_post

7._Chapter_21_electro_post - Electrochemistry Overall...

Info icon This preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter18 Electrochemistry 1 Overall reaction Zn(s) + Cu ( aq) Zn 2+ (aq) + Cu(s) Half reactions Oxidation – loss of electrons Zn(s) Zn 2+ (aq) + 2e 2+ Electrochemistry
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Chapter18 Electrochemistry 2 Daniel Cell If direct contact between the copper ions and zinc metal is avoided, this reaction can be made to do useful work. In voltaic cells direct contact is avoided by physically separating the oxidation and reduction half-reactions. The electrons are forced to flow through an external wire from the zinc half-cell to the copper half- cell. This flow of electrons through an external wire can be used to produce work. A practical voltaic cell is shown below. At the anode, zinc metal is oxidized to zinc ions. Electrons then travel through the external wire to the cathode where copper ions are reduced to copper metal. As the reaction proceeds, Zn 2+ ions are produced at the anode and Cu 2+ ions are consumed at the cathode. To maintain electrical neutrality, sulfate ions must flow through the salt bridge from the half-cell on the left to the half-cell on the right to balance the flow of electrons through the external wire from the anode to cathode.
Image of page 2
Chapter18 Electrochemistry 3 loss of electrons, Oxidation, Anode, -ve Zn(s) Zn 2+ (aq) + 2e (electrons produced) LEO goes (oxidation and anode start with vowels) 2+
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Chapter18 Electrochemistry 4 Cell Notation for Galvanic or voltaic cell 2+ Cell notation Oxidation Reduction
Image of page 4
Chapter18 Electrochemistry 5 The driving force that pushes the negatively charged electrons away form the anode and pulls them toward the cathode is an electrical potential called the electromotive force (emf) or the cell potential (E) or the cell voltage. Cell potential = W = work done (joules) Q charge transferred (coulombs) ( G) Free energy (Joule, J) measure of the spontaneity of a reaction carried out at a constant temperature. If G is negative the reaction is spontaneous If G is positive the reaction is nonspontaneous If G is zero the reaction mixture is at equilibrium G α -nE +ve measurement means a reaction will be spontaneous n = moles of electrons transferred in the reaction E = cell potential (J) G = -nFE F = Faraday constant the electrical charge on one mole of electrons F = 96,500 C/mole e - Where C is the electric charge (coulomb) When 1 C of charge moves between two electrodes that differ in electrical potential by 1 volt, 1 joule of energy is released by the cell and can be used to do electrical work. Volt is potential energy per unit charge V = 1J/1C The cell potential, measured by connecting a voltmeter between the two electrodes, is a measure of the driving force behind this reaction
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Chapter18 Electrochemistry 6 Standard Reduction Potentials Just as a chemical reaction can conceptually be broken into two half-reactions the cell potential can be thought to be composed of two half-cell potentials. The reaction between zinc metal and acid, for example, results from the combination of two half-reactions: Zn(s) Zn 2+ (aq) + 2e - (oxidation) By arbitrarily defining the potential for the half-reaction;
Image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern