Advertisements
Advertisements
प्रश्न
Derive an expression for the Nernst equation.
Advertisements
उत्तर
Nernst equation is the one which relates the cell potential and the concentration of the species involved in an electrochemical reaction.
Let us consider an electrochemical cell for which the overall redox reaction is,
\[\ce{{x}A + {y}B ⇌ {l}C + {m}D}\]
The reaction quotient Q is,
Q = `(["C"]^"l" ["D"]^"m")/(["A"]^"x" ["B"]^"y")` .......(1)
We know that,
∆G = ∆G° + RT ln Q .......(2)
∆G = – nFEcell
∆G° = `-"nFE"_"cell"^∘`
equation (1) becomes
– nFEcell = `-"nFE"_"cell"^∘ + "RT" ln "Q"`
Subsitute the Q value in equation (2)
`-"nFE"_"cell" = -"nFE"_"cell"^∘ + "RT" ln (["C"]^"l" ["D"]^"m")/(["A"]^"x" ["B"]^"y")` …..(3)
Divide the whole equation (3) by (– nF)
Ecell = `"E"_"cell"^∘ - "RT"/"nF" ln ((["C"]^"l" ["D"]^"m")/(["A"]^"x" ["B"]^"y"))`
Ecell = `"E"_"cell"^∘ - (2.303 "RT")/"nF" log ((["C"]^"l" ["D"]^"m")/(["A"]^"x" ["B"]^"y"))` .........(4)
This is called the Nernst equation.
At 25°C (298 K) equation (4) becomes,
Ecell = `"E"_"cell"^∘ - (2.303 xx 8.314 xx 298)/("n"(96500)) log ((["C"]^"l" ["D"]^"m")/(["A"]^"x" ["B"]^"y"))`
Ecell = `"E"_"cell"^∘ - 0.0591/"n" log ((["C"]^"l" ["D"]^"m")/(["A"]^"x" ["B"]^"y"))`
APPEARS IN
संबंधित प्रश्न
The button cell used in watches functions as follows.
\[\ce{Zn_{(s)} + Ag2O_{(s)} + H2O_{(l)} ⇌ 2Ag_{(s)} + Zn^{2+}_{( aq)} + 2OH^-_{( aq)}}\] the half cell potentials are \[\ce{Ag2O_{(s)} + H2O_{(l)} + 2e^- -> 2Ag_{(s)} + 2OH^-_{( aq)}}\] E0 = 0.34 V The cell potential will be
During electrolysis of molten sodium chloride, the time required to produce 0.1 mole of chlorine gas using a current of 3A is ___________.
While charging lead storage battery
Among the following cells
I) Leclanche cell
II) Nickel – Cadmium cell
III) Lead storage battery
IV) Mercury cell
Primary cells are:
For the cell reaction
\[\ce{2Fe^{3+}_{( aq)} + 2l^-_{( aq)} -> 2Fe^{2+}_{( aq)} + l2_{( aq)}}\]
\[\ce{E^0_{cell}}\] = at 298 K. The standard Gibbs energy (∆G°) of the cell reactions is:
A current of 1.608A is passed through 250 mL of 0.5 M solution of copper sulphate for 50 minutes. Calculate the strength of Cu2+ after electrolysis assuming volume to be constant and the current efficiency is 100%.
Calculate the standard emf of the cell: \[\ce{Cd|Cd^{2+}||Cu^{2+}|Cu}\] and determine the cell reaction. The standard reduction potentials of Cu2+|Cu and Cd2+|Cd are 0.34 V and −0.40 volts respectively. Predict the feasibility of the cell reaction.
In fuel cell H2 and O2 react to produce electricity. In the process, H2 gas is oxidised at the anode and O2 at cathode. If 44.8 litre of H2 at 25°C and 1 atm pressure reacts in 10 minutes, what is average current produced? If the entire current is used for electro deposition of Cu from Cu2+, how many grams of deposited?
8.2 × 1012 litres of water is available in a lake. A power reactor using the electrolysis of water in the lake produces electricity at the rate of 2 × 106 Cs−1 at an appropriate voltage. How many years would it like to completely electrolyse the water in the lake? Assume that there is no loss of water except due to electrolysis.
Explain the function of H2 – O2 fuel cell.
