How does the volume of electrolyte affect

the voltage and current in galvanic cells?

and aluminium nitrate from coming into contact The negligible changes in voltage is supported by Introduction with skin which can cause skin and eye irritation. research on the standard cell potentials of the A galvanic cell is an electrochemical cell which electrochemical series. Voltage is calculated by converts chemical energy from spontaneous redox subtracting the electrical potential of the reducing reactions into electrical energy. agent from the electrical potential of the oxidising agent and is determined by the nature of the Aim: To investigate the affect of electrolyte metals. This means the volume of electrolyte will volume on galvanic cells and in particular the not affect voltage as the cell’s electrical potential voltage and current of the cell. will not change.

Current is the flow of electrons from a negatively The slight increase in voltage could be because of charged point to a positively charged point. A errors in the experiment such as varying higher current will mean there is a greater temperature or concentration because of electron flow. measuring limitations or random error with the multimeter. The electrochemical series predicts a In a galvanic cell, voltage is the potential Figure 1.2 - the galvanic cell that was voltage of 2V in the galvanic cell. The experiment difference between the reducing agent and the constructed during the experiment. gave results of 0.42 - 0.5V which is lower than the oxidising agent. It can be calculated with the predicted results. This is because of resistance in equation V = E° oxidising agent - E° reducing 2. The salt bridge was formed by soaking filter the salt bridge and electrodes caused by other agent, where E° is the potential energy of the paper in the potassium nitrate solution. layers of substance on the metal which lowered oxidising/reducing agent which can be found on Potassium nitrate can cause mild skin and eye the voltage values. the electrochemical series. Voltage indicates the irritation. difference between the two electrodes’ ability to 3. The charge and current of the cell were The results showed an increase in current as the form ions. A higher voltage will have a higher recorded. electrolyte volume increased which supported the current. 4. Steps 1-3 were repeated with the 60ml and hypothesis made. As current is determined by the 70ml of the electrolyte solution. The same flow of electrons between two points, a larger Hypothesis: If the volume is increased, the electrode was used for a controlled surface area volume of electrolyte will cause a greater flow of current will increase whilst the voltage will remain and thus more reliable results. electrons and thus a higher current. This is the same. This is because there will be more ions 5. The voltage and current of the three cells was because there is a greater proportion of present in the electrolyte and thus a greater observed and compared. The results can be found electrolyte in contact with the electrode. electron flow between electrodes. Voltage will in figures 2.1 and 2.2. Consequently, more reactions will occur, causing remain the same as the nature of the two a larger amount of electrons flowing from the electrodes and their ability to form ions remains anode to the cathode. the same. Results To improve the accuracy of the experiment, In this experiment, the affect of electrolyte volume results could have been obtained multiple times on current and voltage was tested, thus volume is The results showed current and voltage increased to test the reliability. Furthermore, a more the independent variable and current and voltage as the volume of electrolyte increased. However, reliable multimeter could have been used as three are the dependant variables. Controlled variables the increases in voltage were minuscule and thus different multimeters had to be used before such as electrolyte concentration, temperature can be considered negligible. obtaining reliable results that were close to the and electrode surface area ensured the results predicted values. were valid. However due to measuring limitations, these variables may have varied slightly. Figure 2.2 The affect of electrolyte volume on voltage Methodology 0.5175 1 Equipment: Conclusion 0.495 - scissors 0.4725 0 Three different galvanic cells with aluminium

- 50ml beaker x6 0.45 and copper electrodes and 50, 60 and 70ml of 0 copper sulfate and aluminium nitrate were - multimeter 0.4275 - Voltage constructed. A multimeter was used to measure copper electrode 0.405 the current and voltage of the cell and thus to - aluminium foil 0.3825 observe the affect of electrolyte volume on - potassium nitrate 0.1M 0.36 voltage and current. 50ml 60ml 70ml - aluminium nitrate 1M Volume of Electrolyte The results obtained confirmed the hypothesis, - copper sulfate 1M showing that an increase in electrolyte volume - filter paper will increase the current whilst the voltage will - electrical lead Figure 2.1 remain approximately the same. This is The affect of electrolyte volume on because a larger volume of electrolyte means Method: current more ions are present and thus more electrons 28.75 1. A galvanic cell was constructed using 50ml of will be transferred between the electrodes 22 which causes a higher current. Voltage remains the copper sulfate and aluminium nitrate 23 solution as the electrolyte, like that in figure 18 the same as the nature of the two electrodes 15 1.1 and 1.2. 17.25 remains unchanged and thus the potential difference will stay the same. The results 11.5 showed a small increase in voltage but the Current increase was negligible. This increase could be 5.75 due to experimental errors such measuring limitations causing varying temperatures or 0 random errors caused by the multimeter. 50ml 60ml 70ml Volume of Electrolyte

Figure 1.1 - a galvanic cell was constructed. Discussion

The results of the experiment showed that The aluminium and copper electrodes were cut to current is significantly affected by the volume of equal sizes and sanded to remove oxidised layers electrolyte present in the galvanic cell whilst and impurities on the metal. This ensured the voltage is not. results obtained were reliable. Safety glasses and a References

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