6
Let's write the half-cell equations in standard form as half-cell reductions.
In a table of standard electrode potentials it would silly to write both the reduction and oxidation reactions since that would needlessly double the size of the table.
$$
\begin{align}
\ce{A+ + e- &-> A} &\quad V_\ce{A} \\
\ce{B^{2+} + 2e- &-> B} &\quad ...
4
According to my notes and many sources on the internet, electrons and cations both travel from the anode (A in the image) to the cathode (B in the image).
The idea of the salt bridge is to prevent electrolytes mixing while providing ion flow. When you have a high concentration of inert ions in the salt bridge, cations in the salt bridge will flow into B, ...
3
The main thing to point out is that your question doesn't actually make sense the way you want it to.
What does it mean if a reduction potential is zero? Or positive? Or negative? Is that favorable or not? It turns out we don't specify this at all!
As an example, consider the standard hydrogen electrode and it's reduction potential:
$$\ce{2H+ + 2e- -> ...
3
You have rightfully assumed the reaction takes place in either basic or neutral medium, otherwise $\ce{Cr(OH)3}$ wouldn't be the product.
This automatically suggests $\ce{H+}$ are not used for balancing half reactions.
Your solution is fine for the provided reaction given that chromium(III) hydroxide stays precipitated.
Here I've basically formatted your ...
2
My book tells me to keep the E∘half-cells as they are written in the
tables and simply put them in
Your book is then one of the few books which teaches electrochemistry properly. The sign of the electrode reduction potential is invariant. If reflects the sign of the electrostatic charge of the electrode with respect to hydrogen electrode. I don;t know if ...
2
Take a look at the two half reactions:
$$
\begin{align}
\ce{Ag+(aq) + e- &→ Ag(s)} &\qquad E^\circ &= \pu{0.80 V} \\
\ce{Sn^2+(aq) + 2 e- &→ Sn(s)} &\qquad E^\circ &= \pu{-0.14 V}
\end{align}
$$
If there is an electron for grabs (like the ones in the wire of a voltaic cell), $\ce{Ag+(aq)}$ and $\ce{Sn^2+(aq)}$ are competing for it. ...
2
Yes, the reaction must be taking place for the voltmeter to measure the difference in potential. Remember
$$V = iR$$
thus a voltmeter works by knowing its internal resistance, $R$, and measuring $i$. Also notice that if $i=0$ then $V = 0$, so a voltmeter must have at least some tiny current to work.
The problem with a voltmeter is that you can imagine ...
2
An ideal voltmeter has an infinite resistance, so does not let any current flow in the system. However nothing is ideal in real life, it consumes a very small amount of current to move the magnet and needle arrangement or electronics. An ideal ammeter has zero resistance. Assume that you have a water tank on your ceiling which supplies water to your kitchen ...
2
Free energy is a state function. No matter how you run the reaction, if you start with a certain state (set of concentration) and end with a certain state (set of concentrations at equilibrium), the change will be the same.
The free energy of reaction is the maximal amount of non-pV work (electrical work in this case) the reaction can do. If it does not do ...
2
Rust is a hydrated iron oxide that has a volume greater than the iron it contains. When iron rusts, the oxide grows in layers and curls away from the iron, exposing it to more corrosion.
Phosphoric acid is a moderately strong acid, but it forms an iron phosphate that is insoluble but adherent to iron (and steel). In that sense, phosphoric acid deactivates ...
2
The standard cell potential is temperature-dependent itself, just like the Gibbs free energy. The easiest way to see this is to write the Gibbs free energy in terms of enthalpy, entropy and temperature:
$$\Delta G^\circ = \Delta H^\circ - T \Delta S^\circ$$
This shows you that $\Delta G^\circ$ is strongly temperature dependent (even if $ \Delta H^\circ$ ...
2
It is a bad question because "Metal A is more reactive than Metal B" has no real meaning. It is a vague choice of word, A is more reactive, but with respect to what?
Your logic is correct
Since A is more reactive, it undergoes oxidation to form A2+ ions,
while B2+ ions undergo reduction and form B. From this we can deduce
that A is the anode and B is ...
2
My question is that suppose we have two metals, A and B. A produces +1 ions. B produces +2 ions. Now even if the two have the same tendency to lose or gain electrons, the B plate would be 'more negative'.
That is not a problem because the tendency of the metal to lose or gain electrons has no direct bearing on the reactivity of the metal or the reduction ...
1
Let's subtract the two reactions from each other to simplify things a bit:
$$\ce{2ClF + 2KBr -> 2KF + Cl2 + Br2}\ \ \ \ \ \ \ \ \ \ [1]$$
$$\ce{ClF + 2KBr -> KCl + KF + Br2}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ [2]$$
$$\ce{ClF + KCl -> KF + Cl2}\ \ \ \ \ \ \ \ \ \ \ \ \ \ [3] = [1]-[2]]$$
Now we can discuss [2] and [3] separately by splitting them up ...
1
It is a bit of a tricky question. The trick is in the wording "flow through". The positive ions on the A side do not actually "flow through" the salt bridge from A to B. Rather positive ions exit the salt bridge on the B side to compensate for the cations depositing on the cathode (B). Likewise negative ions exit the salt bridge on the A side to balance the ...
1
My question is that suppose we have to metals, A and B. A produces +1
ions. B produces +2 ions. Now even if the two have the same tendency
to lose or gain electrons, the B plate would be 'more negative'( As in
this plate would have more negative charge). How has the voltage
helped us determine the difference in the tendencies of these two
metals?
...
1
I'm wondering why is it not necessary to mix a metal like Fe into its own solution $\ce{Fe(NO3)2}$ (like you would do when setting up an electrochemical cell)?
First remember what the purpose of your experiment was:
To determine the relative activity of several metals we observed reactions between the metals and aqueous solutions of dissolved metals.
In ...
1
As previous comments said, this isn't a redox reaction.
The patina or corrosion is made of metal salts -- for copper, it's copper oxide, sulfide, carbonate, and perhaps other things. Vinegar readily converts all these to soluble copper acetate.
Most coins are made of metal alloys, and those alloys sometimes contain metals that are attacked by acid. Nickel ...
1
All depends on the cell chemistry and geometry. It is usually a combination of keeping the energy and conversion of the free energy to thermal energy, when reagents diffuse and happen to meet each other. Or, some side reaction with solvent or auxiliary components may occur, like for $\ce{Li-ion}$ cells.
Some primary lithium cells last many years, while some ...
1
The Nernst equation and electrochemical potentials relate to redox systems, not to reagents and products. The forward and reversed reactions are the same redox system.
Imagine you would want to make a galvanical cell with the same electrodes. Flipping the sign would grant you a Nobel price for inventing a perpetuum mobile.
1
The anode is the electrode, where substances are losing electrons and are oxidated.
The cathode is the electrode, where substances are gaining electrons and are reduced.
The tricky part for the memorising is, anodes and cathodes flip the position, when the current is reversed, depending on if
the cell is in the mode of electrolysis
the cell is in the mode ...
1
There is no completed electronic circuit in an electrochemical cell
In an electrochemical cell, the anode is the source of electrons to the external circuit and the cathode is the sink. The circuit of charge transport gets completed by ions traveling inside the cell. A solar cell is different from an electrochemical cell in that their is no net chemical ...
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