Question

A buffer with a pH of 3.95 contains 0.19 M of sodium benzoate and 0.34 M of benzoic acid. What is the concentration of [H,+] in the solution after the addition of 0.060 mol HCl to a final volume of 1.4 L? Assume that any contribution of HCl to the volume is negligible. [H,O+]=

Answer 1

Solution, Contain 0.19 (M) Sodium benzoate and 0.34lm) e buffer of benzoic solution acid. According to the Homderson equation- pH - pka + log sodium benzoate C benzoic acid Where pka = -logra ka = Dissociation Constant of benzoic neid. The given value pH = 3.95 Csodium benzoate = 0.19 (m) e benzoic acid = 0.34 (M). . 3.95=pka + log o lay or, pka = 3.95-0.253 889 = 4.203. Again, 0.060 MOL heL added to the 1.4L buffer solution. , 1.4L Buffer solution Contain = 0.158 0.266 mol Sodium benzoate And 1.4L Buffer solution Contain = 0.34*1.4 = 0.474 mol benzoic acid. COONa COOH Reaction : + Hel = + Nael [Benzoicedir 0.06 mol Benzoic acid mer (0.06 mol ) Sodium benzoate 0.266 mol After the addition of her, the butter solution Contain = (0.474 +0.06) = 0.534 mol Benzoic acid. And the butter solution contain = (0.266-0106) = 0.206 mol loen Sodium benzoate. 1 Concentration & more sodium benzoate pH = pha + log C benzoic acid volume constent er, pH = 4,203 + log 0.206 or, pH = 3.79 we knno pH = -log [H₂ot7 w [ 3ot] - 10-3.796 Hence, Concentration of CH3ot] às equent to 1.624 810-4. - 10-3.79 = 1624x10-4