Question

Enter your answer in the provided box. A buffer that contains 1.00 M base, B, and 0.750 M of its conjugate acid, BH, has a pH of 9.550. What is the pH after 0.0055 mol of HCl is added to 0.500 L of this solution? pH =

I was not given the Kb.

Answer 1

concentration of weak base, [B] = 1.00 M concentration of conjugate acid, [BH] = 0.750 M [base] According to Henderson equation, pH = PK, + logo [conjugate acid] w [B] According to Henderson equation, pH = pK, +logi BH 1.00 M 9.550 = pK, +10g 0.750 M 9.550 = PK, + (0.125) PK, = 9.550 - 0.125 = 9.425 --------- -- --------------------- -- --- = 0.0110M - + 0.0055 mol Concentration of H+ = 0.500 L ICE table: B + H+ (buffer) (HC) I(M): 1.00 0.0110 C(M): -0.0110 -0.0110 E(M): 0.989 BH+ base(buffer) 0.750 +0.0110 0.761 According to Henderson equation, pH = PK, +log [BH] = 9.425 +10. 0.989 M = 9.425 + 108 0.761 M = 9.425 + 0.114 = 9.539