22-11-2012, 04:09 PM
ELECTROCHEMISTRY QUESTION & ANSWERS
[attachment=40677]
1. What is electrochemistry? What is its importance?
Ans: Electrochemistry is the branch of chemistry which deals with the transformation of
electrical energy into Chemical energy and vice-versa. It is the study of phenomena at
electrode solution interfaces. Electrochemistry deals with the relationship between electrical,
chemical phenomena and the laws of interaction of these phenomena .The branch of
electrochemistry is of major technical importance. The laws electrochemistry forms the basis
of electrolysis and electro synthesis. Knowledge of electrochemistry is of immense
importance to study about the causes of destruction of materials caused due to corrosion.
There are two processes where both are interrelated. Electrolysis is one process where
electrical energy causes chemical changes.
2. What is specific, equivalent, molar conductance and cell constant?
Ans: The resistance of a uniform conductor is directly proportional to its length (l) and
inversely proportional to the cross-sectional area (A). Thus,
The proportionality constant (ρ) is called the specific resistance. In the equa- tion (1)
if l = 1 cm and A = 1 cm2, then
R =ρ
Thus specific resistance (ρ) is defined as the resistance of a electrolyte solution of 1 cm
in length and 1 cm2 cross-section i.e. resistance of one cubic centimeter of the electrolytic
solution. The unit of specific resistance is ohm-centimeter.
The reciprocal of specific resistance (ρ) is called specific conductance. This may be
defined as the conductance of one centimeter cube of a material and is denoted by K.
3. What is the equivalent conductance at infinite dilution? How does it varies with conc.
for strong and weak electrolytes?
Ans: On dilution, the volume of electrolyte solution increases. Thus number of ions
furnished by electrolyte per unit volume is decreased. Hence the specific conductance
decreases on progressive dilution.
Equivalent Conductance
Let us consider a weak electrolyte AB, which is ionized as
AB A
+
+ B
_
when the electrolyte solution is diluted, degree of dissociation increased. As a result
conductivity. Is increased If the process of dilution is continued, more and more
electrolyte molecule will undergo dissociation. At that point on further dilution, no more
ions will produce and equivalent conductance will not increase. This limiting value is
known as equivalent conductance at infinite dilution (λ 0 or λ∞) .
For strong electrolyte, equivalent conductance (λ) increases with dilution and cause of this
variation is fundamentally different from weak electrolytes.
Conductivity of an electrolyte depends on the speed of ion and concentration of ion.
The motion of an ionic species in an electric field is retarded by the oppositely charges
ions due to inter ionic attraction. On dilution, the concentration of electrolyte decreases
and the retarding influence of oppositely charged ions decreases. Consequently the
speed of ion increases and equivalent conductance of electrolyte is increased.
4.What is Kohlrausch’s law? Mention its applications?
Ans: Kohlrausch’s law of independent migration of ions At infinite dilution, each ion of an
electrolyte makes a definite contribution to the total equivalent conductance of the
electrolyte, and this contribution is independent of the presence of the other ionic species.
Kohlrausch’s law is applicable to calculate:
1. Equivalent conductance of weak electrolytes at infinite dilution.
2. Calculation of absolute ionic mobility.
3. Calculation of Solubility of sparingly soluble salt.
4. Calculation of degree of ionization.
5. Calculation of ionic product of water.
[attachment=40677]
1. What is electrochemistry? What is its importance?
Ans: Electrochemistry is the branch of chemistry which deals with the transformation of
electrical energy into Chemical energy and vice-versa. It is the study of phenomena at
electrode solution interfaces. Electrochemistry deals with the relationship between electrical,
chemical phenomena and the laws of interaction of these phenomena .The branch of
electrochemistry is of major technical importance. The laws electrochemistry forms the basis
of electrolysis and electro synthesis. Knowledge of electrochemistry is of immense
importance to study about the causes of destruction of materials caused due to corrosion.
There are two processes where both are interrelated. Electrolysis is one process where
electrical energy causes chemical changes.
2. What is specific, equivalent, molar conductance and cell constant?
Ans: The resistance of a uniform conductor is directly proportional to its length (l) and
inversely proportional to the cross-sectional area (A). Thus,
The proportionality constant (ρ) is called the specific resistance. In the equa- tion (1)
if l = 1 cm and A = 1 cm2, then
R =ρ
Thus specific resistance (ρ) is defined as the resistance of a electrolyte solution of 1 cm
in length and 1 cm2 cross-section i.e. resistance of one cubic centimeter of the electrolytic
solution. The unit of specific resistance is ohm-centimeter.
The reciprocal of specific resistance (ρ) is called specific conductance. This may be
defined as the conductance of one centimeter cube of a material and is denoted by K.
3. What is the equivalent conductance at infinite dilution? How does it varies with conc.
for strong and weak electrolytes?
Ans: On dilution, the volume of electrolyte solution increases. Thus number of ions
furnished by electrolyte per unit volume is decreased. Hence the specific conductance
decreases on progressive dilution.
Equivalent Conductance
Let us consider a weak electrolyte AB, which is ionized as
AB A
+
+ B
_
when the electrolyte solution is diluted, degree of dissociation increased. As a result
conductivity. Is increased If the process of dilution is continued, more and more
electrolyte molecule will undergo dissociation. At that point on further dilution, no more
ions will produce and equivalent conductance will not increase. This limiting value is
known as equivalent conductance at infinite dilution (λ 0 or λ∞) .
For strong electrolyte, equivalent conductance (λ) increases with dilution and cause of this
variation is fundamentally different from weak electrolytes.
Conductivity of an electrolyte depends on the speed of ion and concentration of ion.
The motion of an ionic species in an electric field is retarded by the oppositely charges
ions due to inter ionic attraction. On dilution, the concentration of electrolyte decreases
and the retarding influence of oppositely charged ions decreases. Consequently the
speed of ion increases and equivalent conductance of electrolyte is increased.
4.What is Kohlrausch’s law? Mention its applications?
Ans: Kohlrausch’s law of independent migration of ions At infinite dilution, each ion of an
electrolyte makes a definite contribution to the total equivalent conductance of the
electrolyte, and this contribution is independent of the presence of the other ionic species.
Kohlrausch’s law is applicable to calculate:
1. Equivalent conductance of weak electrolytes at infinite dilution.
2. Calculation of absolute ionic mobility.
3. Calculation of Solubility of sparingly soluble salt.
4. Calculation of degree of ionization.
5. Calculation of ionic product of water.