Question

Which solution will show the highest resistance during the passage of current?

• A. $0.05NNaCl$
• B. $2NNaCl$
• C. $0.1NNaCl$
• D. $1NNaCl$

Answer 1

The correct option is B $2NNaCl$

$NaCl$ is a strong electrolyte. These are almost completely dissociated in their aqueous solutions and show high conductance. ​

Factor affecting electrolytic conductance/resistance:
(a) Solute- Solute interaction:
When inter–ionic force of attraction​ between solute is higher, the resistance will be higher. Thus, lower will be the conductance.
$\text{Attractive force}\propto \text{Charge of ions}$

At higher concentration, ​the force of attraction ​between the ions increases which decreases the ​speed of the ions​. Hence, conductance decreases with increase in concentration​.

(b) Solute - solvent interaction:
It is an interaction of a solute with the solvent. It restricts the free motion of ions, thus, decreasing conductance​. It is actually the solvation/ hydration of ions​.
On dilution, the solute - solvent interactions decrease​. Thus, the ionic mobility and ​conductance increases.​

Thus, solution with higher concentration will have high resistance and low conductance.
Hence, option (b) is correct.