Question

The following 8 questions are related to the titration of 153.0 mL of 0.276 M A with 0.698M HCI at 25°C. (K, of A = 2.18E-4, A is a monoprotic base) 1. What would you estimate the initial pH of A to be prior to the addition of any acid? Choose one. A) pH = 7 B) pH is less than 7 C) pH is greater than 7 2. What is the pH after the addition of 15.3 mL of the HCl solution described above? 3. How many moles of HCl were required to titrate this solution of A to the equivalence point? 4. What volume acid, in ml, corresponds to the moles required to reach the equivalence point? 5. What is the pH at the equivalence point? 6. What is the pOH at the equivalence point? Choose one. A) POH = 7 B) POH is less than 7 C) POH is greater than 7 7. What volume (in mL) of HCI would you need to add to reach the half equivalence point? 8. What is the pH at the half equivalence point?

Answer 1

Kb = 2.18x164 pkb = 3.66 : pla = 10.34 1 c) pH is greater than 7 mmolesor A. 153x0:276 = 42.23 mmols of Hu= 15.380.698 = 10.68 Á + H+ HA 42-23. 10.68 0 ' i 31.55 0' 10.68 - PP - P = + 1 ( 9 ) , = 10:34+109 (31:55) 1 pH = 10.81 moles of Hd required - 0.0422 volume of acid = 0.0422 x 1000 0.698 Pret : 60.50mL pH = 1 / (pka_loge ) = 1/2 (10.34 - 1090 196) pH 5.52 en polis greater Han 7 6) volume = 30.25 m $) pH = - 3