Mol wt of nitric acid = 63
Therefore no of moles of acid = 0.063/63 = 0.001
Since no concentration is mentioned I am assuming it is in 1 liter solution.
Thus concentration of nitric acid = 0.001 molar
HNO3 = H+ + NO3-
Since it’s a strong acid taking degree of dissociation 1.
H+ concentration is equal to 0.001 molar
Thus OH- conc. is equal to Kw/ H+
Where Kw is dissociation constant of water = 10^ (-14)
Therefore OH- conc. = 10^(-11)
(please rate if useful)HHhh