1    Why standard hydrogen electrode is called reversible electrode?
The reason is that standard hydrogen electrode can act both as anode as well as cathode in the electrochemical cell.
2    What is the source of electrical energy in a galvanic cell?
In a galvanic cell, the redox reaction is of spontaneous nature. The energy as free energy (∆G) is released in the reaction. This gets converted into the electrical energy.
3     How can the electrode potential of an electrode be increased?
According to Nernst equation, the electrode potential is written as?
                                   E=E0+0.0591/log [Mn+(aq)    
Clearly the electrode potential can be increased by increasing the concentration of the metal ions in solution, thus, it is possible to increase the electrode potential of an electrode by adding a small amount of the same electrolyte in which the electrode is already kept.
4    The equilibrium constant is related to only E0cell and not Ecell. Explain.
We know that at equilibrium point, Ecell becomes zero. It means that cell is not generating any current. But E0cell remains constant under all the conditions. Hence, the equilibrium constant is related only to E0cell.
5    Anhydrous HCl is a bad conductor of electricity but aqueous HCl is a good conductor and why?
Anhydrous HCl is covalent in nature and is a bad conductor. But in aqueous solution, it ionises to give H+ and Cl- ions which conduct the electricity.
     On the basis of E0 values, Na should be more powerful reducing agent than Mg. Why is it possible to carry out the following reduction of Na2O by Mg?
Na2O+Mg       ž          2Na+Mg
On the basis of E0 values, Na is a stronger reducing agent than Mg in solution. However, the given reaction is carried out in solid state. Moreover, under the conditions of experiment, Na is in the vapour phase which helps in the shifting of equilibrium in the forward direction.



7 How does fuel cell operate?
At anode: 2H2(g) + 4OH-(aq)    ž 4H2O+4e-
At cathode: O2(g) + 2H2O(l)+4e -    ž     4OH-(aq)
Net reaction: 2H2(g)+O2(g)         ž    2H2O(l)
8   Which type of metal can be used in cathodic protection of iron against rusting?
The metal which is more electropositive than iron can be used.
Examples are: Mg, Al, Zn.
     Rusting of iron is quicker in saline water than in ordinary water. Explain.
NaCl present in saline water provides Na+ and Cl- ions. These ions help in the flow of current in a cell which is set up on the iron surface. Due to this, process of rusting becomes quicker.
1   Dilution of an electrolyte helps in increasing its electrical conductivity. But it has an adverse effect as well. Comment.
On dilution, Na+ ion and Cl- ions get hydrated. Due to this, their sizes increase but mobility decrease. This causes a decrease in electrical conductivity.
1  What is a primary cell? Given is example.
Primary cell is the one which cannot be recharged and becomes dead over a period of time. An example is dry cell.


Visit www.topposts.in for more and latest news