I am given a question where I have to state which combination of electrodes will result in the greatest voltage and which will result in the lowest voltage. The metals given are Zinc, Copper, Silver and Hydrogen
I calculated the Ecell for each combination and got the following:
Zinc & Hydrogen: 0.76 V
Zinc & Silver: 1.56 V
Zinc & Copper: 1.1 V
Silver & Copper: 0.46 V
Silver & Hydrogen: 0.8 V
Copper & Hydrogen: 0.34 V
Why isn't the lowest voltage Copper and Hydrogen and why isn't the highest voltage Zinc and silver?
4 answers
I know we've talked about this before. Do you have some reason for knowing your answers are not right. Also, I'm still a little confused about how this is to be done; for example, if I use H2 and Ag (as opposed to Ag and H2) the voltage is -0.8 and that would be lower than any listed. But if that is allowed then Ag and Zn would be -1.56v which is even lower. So the reverse of the highest couple would be the lowest. As I say, I'm just not sure about the guidelines of the question. Perhaps you can shed some light on the subject.
Well I'm a bit confused. I have an assignment where I am to do an online lab. First I'm supposed to find the highest and lowest voltage. For all of my Ecell, I got a positive answer. I have another question which says "Explain what a negative voltage on the volt meter means." but I do not have any negatives voltages. So that made me second-guess highest and lowest voltage results
I am also supposed to write out a balanced equation and cell notation equation for each reaction that produced a positive voltage, but all of mine were positive
I think you need to find a way to clarify the question.
As an example of what is missing,
Zn ==> Zn^2+ + 2e Eocell = +0.76
Cu^2+ + 2e ==> Cu Eocell = +0.34
--------------------------------
Zn + Cu^2+ ==> Zn^2+ + Cu and Ecell = about 1.1 v BUT it isn't clear that you can also consider the reverse of that reaction for
Zn^2+ + Cu ==> Zn + Cu^2+ Ecell = about -1.1v.
As to the negative voltage on the voltmeter, that is because the cell is spontaneous in the direction opposite to the physical hook up of the voltmeter. What I mean by that is that the voltmeter is hooked up with the + terminal hooked to the negative terminal of the cell and the - terminal of the voltmeter is hooked to the + terminal of the cell. In other words the electrons are flowing in the opposite direction to the way the voltmeter is wired into the circuit.
As an example of what is missing,
Zn ==> Zn^2+ + 2e Eocell = +0.76
Cu^2+ + 2e ==> Cu Eocell = +0.34
--------------------------------
Zn + Cu^2+ ==> Zn^2+ + Cu and Ecell = about 1.1 v BUT it isn't clear that you can also consider the reverse of that reaction for
Zn^2+ + Cu ==> Zn + Cu^2+ Ecell = about -1.1v.
As to the negative voltage on the voltmeter, that is because the cell is spontaneous in the direction opposite to the physical hook up of the voltmeter. What I mean by that is that the voltmeter is hooked up with the + terminal hooked to the negative terminal of the cell and the - terminal of the voltmeter is hooked to the + terminal of the cell. In other words the electrons are flowing in the opposite direction to the way the voltmeter is wired into the circuit.