Question

Succinic acid is a diprotic acid with formula of HOOCCH2CH2COOH which we can represent as H2R. Suppose a 100.00-mL solution of 0.1000M Na2R is titrated with 0.2000M HCl.

Ka1 for Succinic acid = 6.21 x 10^-5

Ka2 = 2.22 x 10^-8

1. What is the pH after addition of 75.00 mL of 0.2000M HCl to the Na2R solution?

2. What is the pH after addition of 100.00 mL of 0.2000 M HCl to the Na2R solution?

Answer 1

NAZR = 100 ML x0.1 = 10 mmol 0 HCI 75 x0.2 m = 15 mmol Na2B +Hcl - NAHR + Nach Tommol C 15 mmol O . H 10 mmol W 15-10 - 5 mmol NAHR + HCl - Ha B + Nac! o I 10 mmol 5 mmol Remaing 5 mmol E 10-5 5 mmol pH = pka + log Salt (NaHR) acid (tkr) Рқа = Но ка/ -5 pka=-og 6.21x10 pH = 4,21 + 1095 mmol 5mmol pka = 4.21 pH = 4.21

HCl = 100 mL X 0.2 = 20mmol Na2R THE NaHR + Nach 10mmol 20 MMO! 10mmol o 10 mmol Remaing lommer mening 10 mmol formed Natr + HCI - HAR + Naci 10 mmo - 10mmo lommor E 0 0 lommal HR = 10 mmol 200ML 0.05 M ter HR + H+ H 0.05 0.05-x 0.05>>2 Kai = x 0.05-X 6.21x10-5 0.05 re?= 0.3105x105 - 3.105x106. xo 13.105 x156 1.76210x103 pH = -log 1176210 x10-3 pH = 2.15