Engineering Chemistry S Datta

256 ENGINEERING CHEMISTRY
or log K = –
nFE°
2303 . RT
= –
10 × . 5757
0.
0592
= – 9.7246 = – 10 + 0.2754
or Here K = K sp
= Antilog 10. 2754 = 1.886 × 10 –10 mol 2 l –2 .
SHORT QUESTIONS AND ANSWERS
Q. 1. What is galvanic cell or voltaic cell?
Ans. It is a simple device of producing electrical energy by chemical reaction, e.g., Daniel
cell. Such a cell is also known as electrochemical cell.
e
V
Salt bridge
e
SO 4
2–
Zn
Cu
ZnSO 4
Zn ⎯⎯→ Zn +2 + 2e –
Cu 2+ + 2e ⎯⎯→ Cu
CuSO4
(oxidation)
(reduction)
Fig. 10.16
In the above cell Zn-electrode is anode and Cu-electrode is cathode.
Q. 2. What is an electrolytic cell?
Ans. It is a device used for converting electrical energy into chemical energy.
Q. 3. What do you mean by electrode potential (E)?
Ans. It is the tendency of an electrode in a half cell to lose or gain electrons when it is in
contact with the solution of its own ions.
Q. 4. What are reduction and oxidation potentials?
Ans. Reduction potential is the tendency of an electrode in a half cell to gain electrons
and oxidation potential is the tendency of an electrode in a half cell to lose electrons.
Q. 5. What do you mean by standard electrode potential (E°)?
Ans. It is the electrode potential of a metal in contact with its ions when the concentration
of ions is 1 M (1 molar).
Q. 6. What is a salt bridge?
Ans. It is an inverted U-tube containing an electrolyte (e.g., KCl, KNO 3
). It connects
(acts as a bridge) the solutions of the two half cells.
Q. 7. What is the E.M.F. of a cell?
Ans. It is defined as the potential difference between the two terminals of the cell when
no current is drawn from it.