Electrochemical cells - batteries U4 S2 L1 Electrochemical cells - batteries Textbook Readings MHR page 756: Cells and Batteries pages 757-760: Galvanic Cells Textbook Practice Items MHR page 761: items 1, 2a, 3 and 4 page 767: item 8 page 807: item 2

Upon completion of this lesson, you should be able to: define electrochemical cells   draw and label an electrochemical cell to show the anode, cathode, salt bridge, direction of flow of electrons, and direction of flow of ions   use electrochemical cell notation to represent an electrochemical cell   draw and label an electrochemical cell using electrochemical cell notation

Electrochemistry The study of converting chemical energy to electrical energy. vice versa – reversible ~ equilibrium!

Galvanic cell: p 758 a Galvanic, also known as a voltaic cell is a device that converts chemical energy into electrical energy. It is composed of two half cells separated by a wire and a salt bridge (or porous barrier p. 758) Each half cell contains and electrode and an electrolyte. - Usually a metal immersed in a solution of its own ions. Electrons spontaneously flow from the oxidation half cell to the reduction half cell through the wire. The flow of ions occurs through the salt bridge (or porous barrier) to ensure that everything stays neutral

Anode (-) Salt Bridge Cathode (+) electrolyte ZnSO4 (aq) Electrode Electrode electrolyte ZnSO4 (aq) electrolyte CuSO4 (aq)

Porous barrier – Daniell Cell Salt Bridge controls the flow of ions to maintain the electrical neutrality of each half cell. contains a highly soluble ionic solution in which the ions will not interfere with the solutions of each half cell. KNO3 (aq) In an Electrochemical cell: Anions flow toward the anode – negative ions required to balance out the production of cations from the oxidation at the anode. Cations flow toward the cathode – positive ions required to balance out the removal of cations from the reduction the cathode. Porous barrier – Daniell Cell - the porous barrier of the daniell Cell serves to maintain electrical neutrality by allowing ions to flow between the two half cell. (p 758)

Short hand cell notation The anode is always on the left and the cathode is always on the right. The || represents the salt bridge or porous barrier A | represents a phase boundary between the electrode and electrolyte. Anode reaction || cathode reaction Oxidation || reduction Electrode | electrolyte || electrolyte | electrode

For this reaction:     Sketch the electrochemical cell.   Label the anode and cathode.   Assume a salt bridge is used to connect the cells. Suggest an electrolyte for the bridge.   Write the half-reaction equations and the redox reaction equation.   Write the cell notation

Redox involving gases and ions! ~Inert electrodes~ Some redox reactions do not involve solid metals. Creating an electrochemical cell for these reactions will require the use of an inert electrode. An inert electrode is unreactive and serves as a surface for the transfer of electrons for the aqueous or gas phases. Usually inert carbon or platinum electrodes. Zn|Zn2+ || Eu3+,Eu2+ |Pt.

Write the half cell reaction and sketch the electrochemical cell (assume an inert C electrode)

Battery A group of electrochemical cells arranged in series.