In electrochemistry, why is my experimental voltage value of my cell lower than the standard electrode potential? I used zinc and copper as the electrodes and connected zinc sulphate and copper(II) sulphate using a salt bridge. I got 0.85V instead of 1.10V.
I've read that maybe there might be contamination. What contamination might affect the values? Are there any other reasons I should take note of?
Thanks a lot for your help.
How did you measure the voltage? If you used a voltmeter that takes too much power to operate it the small cell can't supply the current needed to operate the meter; therefore, the voltage drops. Also, if the copper and zinc solutions are not 1 M, that will affect the voltage. Good connections are necessary, otherwise you will have a voltage drop across the resistance at the poor connection. Contamination that you mention may affect the concentration of the solutions as above (so they aren't 1 M); also, some contaminants may react with the copper or zinc electrodes themselves.
Would 1 M be 1 mol/dm3?
Thanks, Dr Bob.
Yes, 1 molar = 1 mol/L = 1 mol/1000 cc = 1 mol/cubic decimeter
That's correct, 1 M is equivalent to 1 mol/dm^3, where "dm^3" refers to cubic decimeter. It represents the concentration of a solute in a solution. In this case, a 1 M solution means that there is 1 mole of the solute dissolved in 1 liter of the solution.
By using this concentration, it ensures that the solutions have the same standard concentration for accurate comparison in electrochemical reactions. The standard electrode potentials of different metals are usually determined under standard conditions, which include a standard concentration of 1 M for the metal ion in solution.