Question

Which of the following statements is wrong?
A. The conductance of a solution of 1 cm length having 1 square cm as area of cross section is called a specific conductance.
B. Specific conductance increases while equivalent conductance decreases on progressive dilution.
C. The limiting equivalent conductance of weak electrolytes cannot be determined by the extrapolation of the plot of \[\Lambda \] against concentration.
D. The conductivity of metals is due to the movement of electrons.

Answer 1

Hint: You can solve this question easily by using the basic concepts of electrochemistry. Weak electrolytes are those, which do not dissociate completely, for example – organic acids. Metallic conductors are those which are primarily made up of metals.

Complete step by step answer:
Let us look at the options given in the question –
I. The conductance of a solution of 1 cm length having 1 square cm as area of cross section is called a specific conductance.
The given statement is true.
Specific conductance is denoted by the letter ‘k’.
k = G(l/A), where, G – Conductance, l = length = 1 cm, A = Area = 1 square cm.

II. Specific conductance increases while equivalent conductance decreases on progressive dilution.
The given statement is false.
On dilution, the specific conductance decreases. It is because the number of ions per mL decreases.
On dilution, the equivalent conductance increases. It is because the degree of ionization increases with dilution, which increases the number of ions.

III. The limiting equivalent conductance of weak electrolytes cannot be determined by the extrapolation of the plot of \[\Lambda \] against concentration.
The given statement is true.
For weak electrolytes, the plot of \[\Lambda \] against concentration is not linear and maximum value of molar conductivity cannot be obtained.

IV. The conductivity of metals is due to the movement of electrons.
The given statement is true.
Therefore, the conductance of metallic conductors increases with the number of free electrons.
Also, on increasing the temperature, conductance decreases since vibration in individual kernels increases.

Therefore, the answer is – option (b).

Note: Conductors are primarily of two types –
Metallic conductors –
They are also known as electronic conductors.
This type of conductor conducts electricity without undergoing any decomposition.
For example – metals, graphite, etc.

Electrolytic conductors –
They are also known as ionic conductors.
This type of conductor is liquid or aqueous in nature. It conducts electricity by decomposition of any salt, acid or base in a solvent.
For example – NaCl, KCl, Acetic acid, etc.