3 Pt s Sn 2 aq Sn 4 aq Cu 2 aq Cu s See example 1b on page 12 for help PETER

# 3 pt s sn 2 aq sn 4 aq cu 2 aq cu s see example 1b on

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The galvanic cell consists of a cobalt metal strip in a cobalt (II) chloride solution and a copper strip in a copper (I) chloride solution. PETER STARODUB - PALOS VERDES PENINSULA HIGH SCHOOL3.Pt(s) | Sn2+(aq) , Sn4+(aq) || Cu2+(aq)| Cu(s)(See example 1(b) on page 12 for help.)
CHEM. 2AP UNIT 15 CH. 17 Electrochemistry1405/ 05/2014 DEPENDENCE OF CELL POTENTIAL ON CONCENTRATION OF IONS IN THE CELL At this end of this section you will be able to: Predict the voltage of the cell Ewhen it runs (discharges) and gets weaker and weaker. Determine how to increase the voltage of a galvanic cell by changing the concentrations of the ions. Calculate equilibrium K constants from cell voltages Galvanic cells produce a very small voltage. Nonstandard concentrations though produce a cell voltage that is different from that at standard concentrations (solutions at 1.0 M). It is the difference in concentration that produces the cell potential. The concentration of ions in a Galvanic cell can be other than standard. The concentration of the ions being other than standard will be applied to these 2 situations: When a cell under standard conditions runs and gets weaker until the cell eventually goes dead. Ecell= 0. The Ecellcan be determined at any time as the cell is running. It is said that the cell is discharging.When the concentrations in a galvanic cell are increased before the cell (battery) is used so that more voltage can be obtained and the cell will last longer. The concentrations are deliberately changed to increase the voltage of the cell. **Note: cellis the voltage under standard conditions: 25°C and solutions at 1.0 M. at non-standard conditions, becomesLE CHATELIER’S PRINCIPLE SITUATION 1: WHEN A GALVANIC CELL IS RUNNING AND THE VOLTAGE IS DECREASING (THE CELL IS DISCHARGING) As the cell discharges and current flows from the anode to cathode, the concentrations of the ions will change and as a result Ecellwill change. In fact, the cell will spontaneously discharge until it reaches equilibrium. Equilibrium in a cell means that the forward reaction is no longer happening. At this point Ecellis 0. There is no voltage being produced. ΔGA “dead” battery is one in which the cell reaction has reached equilibrium, and there is no longer any chemical driving force to push electrons through the wire. In other words, at equilibrium, the components in the two cell compartments have the same free energy and G= 0 for the cell reaction at the equilibrium concentrations. The cell no longer has the ability to do work. This is a dead battery.You can use LeChatelier’s Principle to predict if the cell voltage will increase or decrease due to a change in concentration of the ions in solution due to the cell operating. You can use the Nernst Equation to confirm it and to get the actualEcellin volts. Example 1:In the common galvanic cell which we have been discussing, the net reaction is: Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s) cell= V. E. = 0. +1.10 V