If `k_a` of weak acid is `10^-4`,then ` pK_b` will be
4
7
8
10

pK_(a) of a weak acid is defined as :

If pK_(a) of a weak acid is 5, then pK_(b) of the conjugate base will

If the pK_(a) of a weak and acid HA is 4.80 and the pK_(b) of a weak base BOH is 4.78. Then, the pH of an aqeuous solution of the corresponding salt, BA will be