So this is probably going to look like a ridiculously easy question, but I'm stumped. I have searched for hours looking for a formula to use, and I've given up on my text. Question: A 0.1 mol/L aqueous solution of weak monoprotic acid has a hydrogen ion concentration of 0.001 mol/L. The value of the ionization, Ka, for this acid is: a) 10^-6 b) 10^-2 c) 10^-3 d) 10^-5 Now I want to use the formula Ka=[H+] [A-] / [HA] whcih would give me Ka= [0.001] [A-] / [0.1]. The answer makes no sense. I have no idea where to go next. Can anyone point me in the right direction??? THANKS@!