Calculate the pH of the following aqueous solution:
0) 29 M H₂S (pK_a1 = 7.00; pK_a2 = 12.89)

Question

Calculate the pH of the following aqueous solution: 0)29 M H₂S (pK_a1 = 7.00; pK_a2 = 12.89)

Quizplus · Accepted Answer

Since the pKa1 value is lower than the pH of the solution, H₂S will act as an acid and donate a proton to water. The resulting species, ₂S-, is a weak base that will react with water and form hydroxide ions (OH-) and H₂S. H₂S + H2O ⇌ ₂S- + H3O+ Therefore, to determine the pH of the solution, we need to find the concentration of H3O+. Let x be the concentration of H3O+ produced from the dissociation of H₂S. Next, we write the equilibrium expression for the ionization of H₂S, using the Ka1 value: Ka1 = [H3O+][₂S-]/[H₂S] 7.00 = x^2/[H₂S] Since H₂S initially is 0.29 M, and x is much smaller than 0.29 due to the weak nature of the acid, we can approximate [H₂S] = 0.29 M - x. Therefore: 7.00 = x^2/(0.29-x) Solving for x gives x = 1.22×10^-4 M. So: pH = -log[H3O+] = -log(1.22×10^-4) = 3.77 Thus, the correct answer is C.

Calculate the PH of the Following Aqueous Solution