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Now is when the real fun starts! I will use the equation from before and compare the theoretical value, in green, with the experimental value, in yellow. The results are listed in the table and chart below.



Conc. of Zn2+ Theor. Voltage Exp. Voltage
1 M 1.100 V 1.071 V
0.1 M 1.13 V 1.055 V
0.01 M 1.159 V 1.086 V
0.001 M 1.189 V 1.074 V
0.0001 M 1.218 V 1.098 V

As the concentration for the zinc continues to decrease, there seems to be an increase in the voltage produced. The ascent is not as steep or as obvious as it should have been due to numerous experimental errors. I found that varying the the terminal's position in the beaker varies the voltage tremendously. Sometimes the metallic strips weren't rinsed every time they were entered in a new solution and the copper kept corroding in the solution. These factors could have made the voltage consistently lower than its theoretical value.

I've been having difficulties calculating the internal resistance of the battery Vterm = Emf - IRint, because I couldn't easily access the current. It is almost in the league of microamps. I tried to do the next best thing, recording three sample voltages, using a 1,000, 10,000, and 100,000 ohm resistors for each case. I will be show you a couple of the sets for both of our convenience.

1,000 ohms 10,000 ohms 100,000 ohms
1M CuCl, 1M ZnSO4 0.145 V 0.725 V 1.011 V
1M CuCl, 0.1M ZnSO4 0.236 V 0.800 V 1.036 V
1M CuCl, 0.01M ZnSO4 0.200 V 0.768 V 1.035 V
1M CuCl, 0.001M ZnSO4 0.094 V 0.516 V 0.958 V
1M CuCl, 0.0001M ZnSO4 0.100 V 0.502 V 0.890 V









I then used my measurements and the webpage below to approximate the internal resistance of the battery.

Java applet for finding internal resistance

It was calculated to be in the range from 4800-6000 ohms. I cannot make out a specific value, since the solution in the salt bridge eventually evaporates over time. So the lowest value is consistent with the first measurement I made and vice versa. The internal resistance should increase for every trial as the zinc solution becomes more dilute. That should make sense, because the electrons have less ions to jump across. From Ohm's law V/I = R, it is valid to assume that the current is decreasing as the concentration of the Zn2+ solution decreases.
Prepping for the Trail Reality Check The Journey The Final Stop