Question

Part A A beaker with 1.20x10 mL of an acetic acid buffer with a pH of 5.000 is sitting on a benchtop. The total molarity of acid and conjugate base in this buffer is 0.100 M. A student adds 6.10 mL of a 0.340 M HCl solution to the beaker. How much will the pH change? The pK, of acetic acid is 4.740. Express your answer numerically to two decimal places. Use a minus ( - ) sign if the pH has decreased View Available Hint(s) 80 AEQ O ? ApH- Submit

Answer 1

We know that acetic and is a wear acid Since it has pika value = 4.75 Now for a acetic acid buffer solo - pka + log [Conjugate tase] or (Salt) y [cid] 0. (c. 4-3) º E 4 II Given that 4-5 & [Conjugate bare + facia] = 0.1M Let, Conor of acid = x M) So Conjugate sase) : 0.1-x S 5=4.75 + log x. a 1.78 x = 0.1-12 ov, 2.78 x = 0.1 OV, n = 0.03597 So, faci] = 0.03597M Conjugare base) = 0.069M Total volume of some 1,20 x 10 mL 8. 1.20 x 10 ml Sogn contain 0.03597 x 1.20x10 mols acid 1000 = 0,00432 hi

& mots of Conjugare base = 0.064X1.20% 10 1000 = 0.00768 Now, 6.10nf 0.34 M Hg contain 0.34 X 6. 10 mol H+ 100v -0.002074 mots #t

So total mools of acidie H t = 16,00 432 +0.002074) after addition of Hy) - 0.006394 Total volume = (1. 20x 102 +6.10 Juul = 126.10 m to, Molarity of the HT = 0.006394x1000 (M) 126.10 - 0.050706 M So, ft of New soep after awitin of tel = lg (0,050406] = 1.99 Co, Apt = 1. 29-5 = -3.70