Electrochemistry - Electrochemistry Introduction...

This preview shows page 1 - 4 out of 24 pages.

1 Electrochemistry Introduction Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor (a metal or a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between the electrode and the electrolyte or species in solution. Electrochemical Cell: An electrochemical cell is a device used for generating an electromotive force (voltage) and current from chemical reactions. The current is caused by the reactions releasing and accepting electrons at the different ends of a conductor. An electrochemical cell consists of two half-cells. The two half-cells may use the same electrolyte, or they may use different electrolytes. Each half-cell consists of an electrode, and an electrolyte. The chemical reactions in the cell may involve the electrolyte, the electrodes or an external substance (as in fuel cells which may use hydrogen gas as a reactant). In a full electrochemical cell, ions, atoms, or molecules from one half-cell lose electrons (oxidation) to their electrode while ions, atoms, or molecules from the other half-cell gain electrons (reduction) from their electrode. A salt bridge is often employed to provide electrical contact between two half-cells with very different electrolytes—to prevent the solutions from mixing. This can simply be a strip of filter paper soaked in saturated potassium nitrate (V) solution. Other devices for achieving separation of solutions are porous pots and gelled solutions. For example
Image of page 1

Subscribe to view the full document.

2 The half-cell, called the anode, is the site at which the oxidation of zinc occurs as shown below. Zn (s) ----------> Zn +2 (aq) + 2e - During the oxidation of zinc, the zinc electrode will slowly dissolve to produce zinc ions (Zn +2 ), which enter into the solution containing Zn +2 (aq) and SO 4 -2 (aq) ions. The half-cell, called the cathode, is the site at which reduction of copper occurs as shown below. Cu +2 (aq) + 2e - -------> Cu (s) When the reduction of copper ions (Cu +2 ) occurs, copper atoms accumulate on the surface of the solid copper electrode. The reaction in each half-cell does not occur unless the two half cells are connected to each other. Reversible & Irreversible cells: Reversible electrochemical cells are the cells whose cell reactions can be get reversed when an external emf greater than its capacity is applied. (A cell which obeys thermodynamic conditions of reversibility is known as reversible cells).For example
Image of page 2
3 Daniel cell with Capacity 1.1 V, when an external emf of 1.1 V is applied, the cell reaction stops. Zn + Cu +2 ----------> Zn +2 + Cu But when an increased amount of emf greater than 1.1 V is applied, the cell reaction is get reversed. Zn +2 + Cu -------> Zn + Cu +2 A cell of this type can be termed as Reversible cell. Irreversible electrochemical cells are the cells whose cell reactions can not be get reversed when an external emf greater than its capacity is applied. (A cell which does not obey thermodynamic conditions of reversibility is known as irreversible cells). For
Image of page 3

Subscribe to view the full document.

Image of page 4
  • Fall '16
  • Electrochemistry, electrode, Daniel Cell, Electrochemical Series, Reversible cell

{[ 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