Calculate the equilibrium constant for the reaction:
Zn + Cd2+ (aq) → Zn2+ (aq) + Cd (E°cell = 0.36 V)

we have given that
Ecell0 =0.36V
thus equilibrium constant is 

logk = nEcel00.059
 n=2 

k =antilog nEcel00.059

k =1.596 x 1012

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What are fuel cells? Write the electrode reactions of a fuel cell which uses the reaction of hydrogen with oxygen.

A device to convert chemical energy of fuel into electrical energy is called fuel cell.


Hydrogen-oxygen fuel cell: The cell consists of three compartments separated from one another by porous electrode. The hydrogen gas is fed into one compartment and the oxygen gas is fed into another compartment. These gases then diffuse slowly through the electrodes and react with an electrolyte that is in the central compartment. The electrodes are made of a conducting material, such as graphite, with a sprinkling of platinum to act as a catalyst, and the electrolyte is an aqueous solution of a base. The reactions are
Cathode: O2(g) + 2H2O(l) + 4e-----> 4OH(aq)
Anode: 2H2 (g) + 4OH(aq)-----> 4H2O(l) + 4e
Overall reaction being:

2H2(g) + O2(g) ----->2H2O(l )
Advantages: (i) Fuel cells are efficient and free from pollution.
(ii) The only product in the reaction of fuel cell is water which can be removed and the astronauts of a spacecraft can drink it.
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What is normal hydrogen electrode? Discuss its uses.

Definition: The standard hydrogen electrode is the standard measurement of electrode potential for the thermodynamic scale of redox potentials.

The standard is determined by the potential of a platinum electrode in the redox half reaction

2 H+(aq) + 2 e- → H2(g) at 25 °C.

The standard hydrogen electrode is often abbreviated SHE.

Also Known As: normal hydrogen electrode or NHE

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On the basis of the standard electrode potential values stated for acid solution. Predict whether Ti4+ species may be used to oxidise FeII to FeIII.
Reaction: E°/V TiIV + e → Ti3+ + 0.01
Fe3+ + e → Fe2+ + 0.77


Ti4+ would not oxidize Fe+2 . since the standard electrode potential of iron is high as compare to the titanuim standard electrode potential.

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Predict the products of electrolysis obtained at the electrodes in each case when the electrodes used are of platinum.
(i) An aqueous solution of AgNO3.
(ii) An aqueous solution of H2SO4.


(i)
Reaction in solution
AgNO3               ↔     Ag +    +        NO3
H2O             ↔     H+       +        OH
Reaction at cathode
Ag+   +          e       →      Ag
Reaction at anode
Due to platinum electrode self of ionization of water will take place 
H2O   →     2H+    +        1/2O2(g)   +  2e
Hence Ag will deposit at cathode and O2 gas will generate at anode

(ii)
Reaction in solution
H2SO4                          ↔     2H +  +        SO42–
H2O             ↔     H+       +        OH
Reaction at cathode
H+      +          e       →      ½ H2
Reaction at anode
Due to platinum electrode self of ionization of water will take place 
H2O   →     2H+    +        1/2O2(g)   +  2e
Hence H2 gas will generate at cathode and O2 gas will generate at anode
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