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?
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
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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.
To determine which combination of electrodes will result in the greatest and lowest voltage, we need to understand the concept of standard electrode potential (E°).
Standard electrode potential is a measure of the tendency of an electrode to gain or lose electrons, expressed in volts. The more positive the value of E°, the greater the tendency of that electrode to undergo reduction (gain electrons) and act as a cathode. On the other hand, the more negative the value of E°, the greater the tendency to undergo oxidation (lose electrons) and act as an anode.
Now, let's analyze the given values of Ecell for each combination of electrodes:
1. Zinc & Hydrogen: 0.76 V
2. Zinc & Silver: 1.56 V
3. Zinc & Copper: 1.1 V
4. Silver & Copper: 0.46 V
5. Silver & Hydrogen: 0.8 V
6. Copper & Hydrogen: 0.34 V
In the given options, the lowest voltage is not Copper and Hydrogen (0.34 V) because the Ecell values are not solely determined by the individual standard electrode potentials of the metals involved. It is important to consider the redox reactions that occur at the electrodes.
In order to determine the Ecell for a combination, we need to subtract the standard electrode potential of the anode (oxidation half-reaction) from the standard electrode potential of the cathode (reduction half-reaction). The larger the positive difference, the greater the potential difference (voltage) between the two electrodes.
Let's compare the standard electrode potentials of each metal involved in the above combinations:
- Zinc: -0.76 V (anode)
- Copper: +0.34 V (cathode)
- Silver: +0.8 V (cathode)
- Hydrogen: 0.00 V (anode)
From the given values, we can conclude that the standard electrode potential of Zinc (-0.76 V) is more negative than the copper’s (+0.34 V) and silver’s (+0.8 V) standard electrode potentials. This means that it has a higher tendency to undergo oxidation (lose electrons) compared to copper and silver.
Therefore, the lowest voltage combination is Copper & Hydrogen with an Ecell of 0.34 V, not Copper & Silver as initially expected.
Similarly, when comparing the standard electrode potentials, we see that the standard electrode potential of Silver (+0.8 V) is greater than the standard electrode potential of Zinc (-0.76V). Thus, the highest voltage combination is Zinc & Silver with an Ecell of 1.56 V, not Zinc & Hydrogen.
In summary, the lowest voltage combination is Copper & Hydrogen (0.34 V), and the highest voltage combination is Zinc & Silver (1.56 V), based on the comparison of their standard electrode potentials.