9.已知 _(b)(N(H)_(3))=1.8times (10)^-5, 则其共轭酸的Ka值为························............................... ()-|||-(A) https:/img.zuoyebang.cc/zyb_a58b1d601983f833843d0b48fd58cb79.jpg.8times (10)^-9-|||-(B) https:/img.zuoyebang.cc/zyb_a58b1d601983f833843d0b48fd58cb79.jpg.8times (10)^-10-|||-(C) .6times (10)^-10-|||-(D) .6times (10)^-5