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Do I use the Nernst equation when the concentrations of electrolyte in both half cells are equal?

Yes, you still use the Nernst equation, but one of your implicit assumptions is not correct. A point about the Nernst equation that often confuses people is that, at first glance, it doesn't predict ...
orthocresol's user avatar
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What pressure units should be used when calculating electrode potential with Nernst equation?

Just as you are supposed to use activity instead of concentration for dissolved components when applying Nernst equation, you are also supposed to use fugacity instead of the partial pressure for the ...
andselisk's user avatar
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N in Nernst Equation

The Nernst equation is as follows, \begin{align*} E_\text{red}&=E_\text{red}^{0}-\frac{RT}{nF}\ln{\left(\frac{c_\text{red}}{c_\text{oxi}}\right)}. \end{align*} where $c$ is the concentration ...
Ava's user avatar
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Is there a better equation than the Nernst equation for low concentrations?

The Nernst equation does not need a replacement for low concentrations. Yes the limit is $\infty$, which essentially means you can't realistically have zero concentration of anything. We may think of ...
Ivan Neretin's user avatar
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Deriving Nernst Equation for a hydrogen-oxygen Fuel cell

Rather than pointing whether the assumptions are correct or incorrect, I will show you a general method to obtain the Nernst's equation for any system. It is a more systematic and formal approach, ...
Metal Storm's user avatar
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Why is cell potential an intensive property?

The simple mental test for the property being intensive or extensive is, what happens if you make the all the system twice as big. If the property remains the same, like concentration, or the cell ...
Poutnik's user avatar
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What is the equivalence point in the context of a redox titration?

As the ongoing reaction is $$\ce{5 Fe^2+(aq) + MnO4-(aq) + 8 H+(aq) -> 5 Fe^3+(aq) + Mn^2+(aq) + 4 H2O(l)}$$ the point of equivalence is when the initial molar amount of $\ce{MnO4-(aq)}$ is equal ...
Poutnik's user avatar
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Question on Nernst equation

Let assume the classical representative of cells – the Daniell's cell: $$\ce{Zn(s)}|\ce{ZnSO4(aq)}||\ce{CuSO4(aq)}|\ce{Cu(s)}$$ \begin{align} E_\mathrm{cell} &= \Delta E^{\circ} + \frac{RT}{nF} \...
Poutnik's user avatar
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How exactly does the Nernst equation account for temperature?

There are two temperature dependences involved in the Nernst equation. The explicit one $$\frac{RT}{nF}\ln{a}\tag{1}$$ and the implicit one $$\begin{align} E^\circ(T) &= \frac{-\Delta_\mathrm rG^\...
Poutnik's user avatar
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Conditions for spontaneity of redox reaction among redox couples with equal standard reduction potentials

Yes, it is possible to construct two half cells with the same standard reduction potentials. For example, we can half cells made of copper dipping in copper sulfate solution. The caveat is that if ...
AChem's user avatar
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Electrode potential for saturated silver carbonate solution

Where is the problem? Let's call $s$ the solubility of $\ce{Ag2CO3}$. As a consequence $[\ce{Ag+}] = 2s,$ and $[\ce{CO3^2-}] = s.$ So the solubility product is $$K_\mathrm{s} = [\ce{Ag+}]^2\,[\ce{CO3^...
Maurice's user avatar
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Unit derivation concerning Nernst equation

M. Farooq have given good description of how to analyse units in a equation. Therefore, your assumption of the unit of $\dfrac{RT}{nF}$ should be Volts is correct. However, your question is not to ...
Mathew Mahindaratne's user avatar
3 votes

Application of Nernst Equation in Potentiometric titration of Fe2+ with Ce4+

It is an interesting question. Daniel Harris is revising his book with my former mentor. Hope he clarifies this section in the revised version. Your point number 1 is misleading. The reason is that ...
AChem's user avatar
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2 votes

What exactly is Q in the Nerst equation for a ¨lemon battery¨ of Cu and Zn in varying concentrations of acid?

The 'Q' in Nerst equation is the same Q which you might've used while dealing with chemical equilibria, otherwise known as the Reaction Quotient. The expression is same as the equilibrium constant (K) ...
Berry Holmes's user avatar
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Nernst equation calculations

For (1), I think you made the mistake of using a different value for overall cell potential when you worked backwards. Because if you use the correct overall cell potential, you get $K = 31.52$, your $...
tumblewush's user avatar
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Calculate the cathode electrode potential in this redox reaction

Zhe's answer is the best. Though, I will try to offer a different (mathematical) approach, which will hopefully enable you to see the answer yourself, or rather, verify that your book's solution is ...
Gaurang Tandon's user avatar
2 votes

Calculate the cathode electrode potential in this redox reaction

The equation that corresponds to the standard reduction potential is: $$\ce{Mg^{2+} + 2e- -> Mg}$$ Notice that this is not the actual half reaction in your total equation, where magnesium is ...
Zhe's user avatar
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Proof of the chemical potential formula

(a) The idea of potentials is familiar from mechanical and electrical systems. In an electric field the work required to move a charge $q$ from one location with potential $\theta_1$ to one with $\...
porphyrin's user avatar
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Proof of the chemical potential formula

The Sackur-Tetrode equation can be written as $$S^{Trans}=R\ln \left( \frac{e}{C\Lambda^3} \right)$$ where $C$ is the concentration and $\Lambda$ the thermal wavelength. You can rewrite this as $$S^{...
Jan Jensen's user avatar
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Why is the reaction quotient Q always equal to one at standard state?

As already said in the comments, you cannot use any unit you want in the reaction quotient; it has to be formulated in terms of activity (for solutes) or fugacity (for gases). The "standard state&...
user68044's user avatar
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Nernst Equation for Lithium ion battery

The Nernst equation for the anode is :$$E_a = E°_a + \frac{RT}{F}ln{\frac{[Li^+]_e [C_6]_s}{[LiC_6]_s}}$$ where the concentrations $[C_6]_s$ and $[LiC_6]_s$ are defined in the solid phase of the ...
Maurice's user avatar
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2 votes

Unit derivation concerning Nernst equation

You should read the article "Can One Take the Logarithm or the Sine of a Dimensioned Quantity or a Unit? Dimensional Analysis Involving Transcendental Functions" Here The concepts mentioned ...
AChem's user avatar
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2 votes

Can an electrode run out of the active species?

Yes, it will absolutely run out. To put it simply, this is a battery, and it will run out of juice like any other battery. You're also correct about which reactant would run out first. The hydrogen ...
anon's user avatar
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Inconsistency in between Nernst Equation and Gibbs Free Energy Equation

Rather than being an inconsistency, it has to do with the freedom of choosing a mathematical expression for the chemical potential that is more convenient to you. A general expression for the chemical ...
Metal Storm's user avatar
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Effect of temperature on voltage of a galvanic cell can't use Nernst equation?

TL;DR; version: Testing the EMF dependence on temperature does make sense, because it is not the matter just of the term $\dfrac{RT}{nF} \ln {Q}$. But you cannot use the Nernst equation directly as ...
Poutnik's user avatar
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Gaseous reactant in Nernst equation

The Nernst equation does involve partial pressure on involved redox-active gas, but the writers of textbooks must mention it. You should always refer to the source of questioned info for others to ...
Poutnik's user avatar
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What would happen to the cell potential if two half cells of a galvanic cell were at different temperatures?

Good experimental design means ensuring that you have repeatable and well defined experimental conditions - by not adequately controlling the temperature of the two half-cells you've introduced the ...
Noteless Scholar's user avatar
1 vote

Activities and molar concentrations

Most thermodynamic equations are derived assuming a perfect gas or ideal solution. However, for real a solution the chemical potential $\mu_i=\mu^0_i +RT\ln(x_i)$ may not be accurate for the solvent ...
porphyrin's user avatar
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1 vote

Nernst equation and equilibrium

problem where one is supposed to calculate the concentration of Fe3+ ions after a solution containing Fe2+ was titrated using acidified permanganate, There are several things which may be ...
AChem's user avatar
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1 vote

Can the rate of reaction of a Voltaic/Galvanic cell be determined theoretically?

Since battery scientists got Nobel this week, this question is worth pondering. It is not a trivial question. However consider this question: A car battery has 12 V, whereas 9 V cells are also common....
AChem's user avatar
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