Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): For a weak monobasic acid at concentration C , the acid dissociation constant K_ a is given by the expression K_ a = C ( _ m ^ )^2 _ m ( _ m ^ - _ m ) . Reason (R): The degree of dissociation = _ m _ m ^ and according to Ostwald's dilution law, K_ a = C ^2 1 - . In the light of the above statements

Step-by-step solution

The Reason statement correctly provides the standard formulas for the degree of dissociation ( ) in terms of molar conductivities and the acid dissociation constant ( K_ a ) from Ostwald's dilution law. Therefore, Reason (R) is true. To evaluate the Assertion, substitute = _ m _ m ^ into the expression 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 ) The expression given in the Assertion has the numerator and denominator terms inco