For strong electrolytes, the plot of molar conductivity ( _m ) versus the square root of concentration ( c ) yields a straight line. If the y -intercepts of these plots for HCl , NaCl , and NaCN are P , Q , and R respectively, which of the following expressions gives the limiting molar conductivity of HCN ?

Step-by-step solution

According to the Debye-Huckel-Onsager equation, the y -intercept of a _m versus c plot represents the limiting molar conductivity ( _m^0 ) of the electrolyte. Thus, we are given: _m^0( HCl ) = P _m^0( NaCl ) = Q _m^0( NaCN ) = R According to Kohlrausch's law of independent migration of ions, the limiting molar conductivity of a weak electrolyte like HCN can be calculated from strong electrolytes: _m^0( HCN ) = ^0( H ^+) + ^0( CN ^-) By adding and subtracting the limiting molar conductivities of the respective ions,