COMEDK20269 May 2026Morning ShiftChemistryElectrochemistryActual
Identify the correct mathematical expression which represents the variation in molar conductivity of a weak acid having concentration C and ionisation constant K_a ( _m^ = molar conductivity at infinite dilution, _m = molar conductivity at concentration C)
Options
- AK_a = _m^2 C / _m^ ( _m^ - _m)
- BK_a = _m _m^ - ( _m^ )^2 + _m^2 C
- C_m + _m^ + K_a C^ 1 2 = 0
- DK_a = _m^2 C / _m^ ( _m^ + _m)
Correct answer
A. K_a = _m^2 C / _m^ ( _m^ - _m)
Step-by-step solution
The degree of dissociation for a weak electrolyte is given by: = _m _m^ For a weak acid, the ionisation constant K_a is given by Ostwald's dilution law: K_a = C ^2 1 - Substituting the expression for into the equation for K_a : K_a = C ( _m _m^ )^2 1 - _m _m^ K_a = C _m^2 ( _m^ )^2 _m^ - _m _m^ K_a = C _m^2 _m^ ( _m^ - _m) Answer: K_a = _m^2 C / _m^ ( _m^ - _m)