ï»¿ Prove that the free energy (ΔG) and the emf of an electro-chemical cell are related byΔG = – nFE0. from Chemistry Electrochemistry Class 12 Nagaland Board

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Class 10 Class 12
Prove that the free energy (ΔG) and the emf of an electro-chemical cell are related by
ΔG = – nFE0.

The change in free energy is equal to the useful work done in a reversible process at constant temperature and pressure
ΔG = Wnet ...(i)
In an electrochemical cell and work obtained is equal to the charge transferred multiplied by the potential difference:
Welectrical = – nFE ...(ii)
The negative sign appears because the work is done by the charge. In equation (ii) n is the moles of electrons gained or lost in redox reaction and F is the Faraday constant.
In a cell when only electric work is done, then
Wnet= WeIectrical = – nFE ...(iii)
From relation (i) and (iii), we have
ΔG = – nFE
or ΔG = – mFE°cell.

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Can you store copper sulphate solutions in a Zinc pot?

No. Because zinc is more reactive than copper and thus holes will be developed in zinc pot.

Cu2+(aq) + Zn(s) → Zn2+ (aq) + Cu(s)
1384 Views

Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10.

For hydrogen electrode, ,
given that      pH = 10
use formula [H+] = 10–pH
so that  [H+] = 10−10 M
Electrode reaction will
H+  + e –  →1/2 H2
Use the formula

1279 Views

Calculate the emf of the cell in which the following reaction takes place:
Ni(s) + 2Ag+ (0.002 M) $\to$ Ni2+ (0.160 M) + 2Ag(s)
Given that

$\mathrm{Ni}\left(\mathrm{s}\right)+2{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)\to {\mathrm{Ni}}^{2+}\left(\mathrm{aq}\right)+2\mathrm{As}\left(\mathrm{s}\right)$

or

The equation is also written as

or

= 1.05 V – 0.0295 x log 80

= 1.05 V – 0.0295 x 1.9031

= 1.05 V – 0.056 = 0.99 V.

1585 Views

Consult the table of standard electrode potentials and suggest three substance that can oxidize ferrous ions under suitable conditions.

oxidation of ferrous ion means :

Fe2+--> Fe3+ +e-
Any substance which standard electrode potential is more than that of Fe+3 /F+2 can oxidise ferrous ions.
(refer to the table given in book)

The EMF of the substance whose reduction potentials greater than 0.77V will oxidised ferrous ion.
for example Br2, Cl2,and F2 .

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How would you determine the standard electrode potential of the system Mg2+/Mg?