 # Specific conductivity, Equivalent conductivity

• Specific conductance (K):
(i) In C.G.S system: The conducting power of all the ions that are present in 1 cm3 of a solution is called specific conductance.
(ii) In M.K.S: The conducting power of all the ions that are present in 1 m3 of a solution is called specific conductance.
• In case of conductance (G) volume is not restricted but in case of specific conductance (K) volume of solution is restricted to 1 cm3
• Effect of dilution:
(i) Upon dilution number of ions increases therefore conductance increases
(ii) Upon dilution number of ions present in unit volume decreases therefore specific conductance decreases
• Conductance depends upon following factors
(a) Greater the number of ions higher the conductance.
(b) When number of ions are same greater the charge of the ion higher is the conductance.
(c) When number of ions and charge are equal smaller the size of the ion in aqueous solution greater is the conductivity.
(d) Conductance order Cs+ > Rb+ > K+ > Na+ > Li+  → Big size of Li+ ion in aqueous solution due to "solvation"
• Equivalent conductance (Λequi): The conducting power of all the ions in 1 gram equivalent of electrolyte present in a solution of any volume is called equivalent conductance.
• Relationship between Λequi & K:
Case(i): 1 GEq of an electrolyte is present in 1 cm3 of solution.
∴ Λc = K
Case (ii): 1 GEq of an electrolyte is present in V cm3 of solution.
∴ Λequi = K × V
Where V is volume of electrolytic solution in cm3 which contain 1 GEq of electrolyte
Case (iii): Units for Λc: ohm−1 cm2 gram equi−1 (C.G.S)
ohm−1 m2 gram equi−1 (M.K.S)
• Effect of dilution: Up on dilution equivalent conductance increases (because here increase in volume is more than decrease in K)
• Relationship between equivalent conductance and normality:
(i) In C.G.S system \wedge_{equi}=\frac{K\times 100}{N}
Units: ohm−1 cm2 gram equi−1
(ii) In M.K.S system \wedge_{equi}=\frac{K}{1000\times N}

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1. Specific Conductivity (K):
It is the reciprocal of specific resistance.
\tt k=\frac{1}{\rho}=\frac{l}{R.a}=G\times\frac{l}{a}=G\times cell\ constant \left(G^\star\right)
(\tt \frac{l}{a} = cell constant)

2. Equivalent Conductivity (∧eq)
\tt \wedge_{eq}=\frac{k\times1000}{N}

where, N = Normality.