what causes experimental values to differ from theoretical values? take zn-cu cell voltage for example.?

Question

I have a zn-cu electrochemical cell. Textbooks say that the voltage across this cell should be 1.1V. But when i experiment with the cell i got a lower voltage of 0.9. Why is this so?

I have a zn-cu electrochemical cell. Textbooks say that the voltage across this cell should be 1.1V. But when i experiment with the cell i got a lower voltage of 0.9. Why is this so?

Are there factors that affect the voltage of the cell? Or should the cell have been constructed under certain standard conditions? For eg, the electrolytes should be kept at room temperature etc

Are there factors that affect the voltage of the cell? Or should the cell have been constructed under certain standard conditions? For eg, the electrolytes should be kept at room temperature etc

Answer 1

yes under certain conditions
temperature=298 K
molarity=1mol/dm^3
pressure=1atm
are the standard conditions
for measuring the voltage of standard cell

Answer 2

There are so many possible reasons for that low value.

-Resistance of the wires attached to your electrode and the volmeter you have used will significantly lower down the potential.

-Purity of your Zn and Cu will also affect.

Cleaning the oxidized outer part of electrodes will also help.

Your set-up is galvanic, try to make it electrolytic by applying external voltage in a little while to activate the electrodes.

-Assuming the concentration is correct and the temperature condition is not given on the text, try to warm your solution.

Answer 3

Theoretical values assume ideal, isolated environments and accurate models but in reality, you don't have this.

Your percent difference is a bit high but it could be that the cell isn't as charged as it could be or the equipment you are using to measure the voltage introduces some error.

Answer 4

I would suspect the limited mobility of the positive ions affects the voltage. In the theoretical case, the charges can magically arrange themselves instantaneously.