To determine the effect of temperature and concentration of electrolyte in a Galvanic cell.HYPOTHESIS:I predicted that voltage produced by the galvanic cell would decrease as the temperature increases, according to the Nernst equation. As for concentration, with reducing the concentration of electrolytes in the galvanic cell would reduce the voltage produced because there will be less abundance of reactant.EQUIPMENT:50ml or 100ml beakerLoggerPro, with thermometer probeThermometerVoltmeterHot platePorous cup or Salt bridge1.
0M Zinc Sulfate1.0M Copper Sulfate0.1M Zinc Sulfate0.1M Copper SulfateZinc metalCopper metalVARIABLES:Independent VariablesTemperature of the electrolytes (10°C to 70°C), Concentration of electrolytes (1.0M/0.
1M CuSO4 and 1.0M/0.1M ZnSO4)Dependent VariablesVoltage produced, in VControlled VariablesPressureThe experiment was conducted in the same room, at 101 kPA. Changing the pressure would also affect the voltage, keeping in mind that it would change the standard conditions (even though, temperature of the electrolytes are changing) for the conductivity to occur.
Volumes of electrolytesSince I want to keep my data as accurate as possible, in determining the effect of modifying concentrations and temperatures, I will be using 40mL of zinc sulfate and 20mL of copper sulfate inside the porous cup. Anode and CathodeI will be using the Zinc and Copper metals as my electrodes throughout, since the electrolytes we were supplied with had components of the the zinc and copper ion in it– which is essential for the redox reaction to take place.PROCEDURE:A standard Galvanic cell was created, using approximately 20 mL of 1.00M zinc sulfate, that was diluted with 10 mL of water, in a beaker. 1.00M copper sulfate EQUATIONS:At the anode (negative electrode), zinc is oxidised to zinc ions (Zn2+), and at the cathode (positive electrode), copper ions (Cu2+) are reduced to metallic copper. The salt bridge allows anions (negative ions) to travel to the anode to complete the circuit.
It also allows cations (positive ions) to move to the cathode, and balance the charge imbalance caused by the movement of anions. The sulfate ion (SO42-) is a spectator ion, and does not react, but is present in the electrolytes.However in this investigation, a porous cup was used instead of a salt beaker, in one beaker. The porous cup contained the positive electrode (copper ions) and was placed inside the beaker, that contained the zinc sulfate electrolyte, with the anode submerged in the solution.
The half reactions and overall reaction of a zinc/copper galvanic cell are:At the anode:Zn(s) ? Zn2+(aq) + 2e-(1)At the cathode:Cu2+(aq) + 2e- ? Cu(s)(2)Overall reaction:Zn(s) + Cu2+(aq) ? Zn2+(aq) + Cu(s)(3) The Nernst equation is used to predict the voltage potential of a galvanic cell at non- standard temperatures and concentrations (Wikipedia 2016). The Nernst equation is: Ecell = Eocell – (RT/zF) × ln(Qr ) (4)where Ecell = voltage of cell under non-standard (because we are changing the temperature) conditions, Eocell = standard cell potential in V, R = universal gas constant (8.314472 J K-1 mol-1), T = temperature in Kelvin, z = the number of moles of electrons transferred in reaction, F = Faraday constant (96,485.34 C mol-1), and Qr = the reaction quotient. Where, the standard cell potential for copper and zinc is a available value.