In order to completely neutralize 20 mL of a solution of HCl 0.1 M, 40 mL of a solution of NaOH must be added. What is the M of the NaOH solution? What will be concentration of HS- in a 0.1 M H2S solution when 0.05 M H2SO4 is added to it? (Ka1 & Ka2 are dissociation constants of H2S)