Final answer:
The acid dissociation constant (Ka) for a monoprotic weak acid with a 0.1 M solution and a pH of 6 is 1 x 10^-7.
Step-by-step explanation:
The acid dissociation constant (Ka) of a monoprotic weak acid can be determined using the pH of its solution. For a 0.1 M solution with a pH of 6, the concenration of hydrogen ions [H+] can be calculated using the pH formula, pH = -log[H+]. Given that pH is 6, [H+] is 10-6 M. Assuming the weak acid dissociates according to HA ⇌ H+ + A-, at equilibrium [H+] is equal to [A-] and [HA] is 0.1 M - [H+]. Since the concentration of H+ is much smaller compared to the initial concentration of the acid, we can approximate [HA] to remain 0.1 M. The Ka is given by Ka = [H+][A-]/[HA]. We plug in our values to get Ka = (10-6)(10-6)/0.1 which simplifies to 1 x10-7.