(b) the conductivity of a 0.01 mol dm–3 solution of a monobasic organic acid in water is 5.07 × 10–2 s m–1. if the molar conductance at infinite dilution (λ°) of aqueous sodium chloride, sodium formate and hydrochloric acid are 1.264 × 10–2, 1.046 × 10–2 and 4.261 × 10–2 respectively at 25°c determine the acid dissociation constant and the pka for the acid.

Explanation:

The given data is as follows.

   (NaCl) =

   (H-O=C-ONO) =

   (HCl) =

Conductivity of monobasic acid is

     Concentration = 0.01

Therefore, molar conductivity () of monobasic acid is calculated as follows.

                                  =

                                 =

                                 =

Also, =

                            =

                            =

Relation between degree of dissociation and molar conductivity is as follows.

                             =

                             = 0.1254

Whereas relation between acid dissociation constant and degree of dissociation is as follows.

                     K =

Putting the values into the above formula we get the following.

                     K =

                        =

                        =

                       =

Hence, the acid dissociation constant is .

Also, relation between and is as follows.

                              =

                              = 3.7454

Therefore, value of is 3.7454.