12) Caleulate the pH of a solution that is made by mixing 0.80 Lof 0.30 M formic
ID: 587090 • Letter: 1
Question
12) Caleulate the pH of a solution that is made by mixing 0.80 Lof 0.30 M formic acid (HCOOH Kp1.77x10s) and0.90 L of 0.20 M sodium formate (NaHCOO). Hint don'tforget that you are mixing, and so each is diluted upon mixing) 13) Explain how a buffer solution can stabilize the pH against the addition of acid, base, or additional solvent (dilution). [Hint: Look at the H-H equation] 14) A 25 mL sample of a sulfuric acid solution was titrated to completion with 34.55 ml of 0.1020 M sodium hydroxide. What was the concentration of the sulfuric acid? [Hint: You don'tneed to account for any dilution during the titration to solve this problem. Also, write the balanced reaction for sulfuric acid and sodium hydroxide] 15) If you add 20 mg AgOH to 1 Lof water, will all of the AgOH dissolve?Explanation / Answer
Q12
mol of formic acid = MV = 0.3*0.8 = 0.24 mol
pKa = -log(Ka) = -log(1.77*10^-4) =3.75
mol of Naformate = MV = 0.2*0.9 = 0.18 mol
Vfinal = V1+V2 = 0.8+0.9 = 1.7 L
recalculate
[formica cid] = mol/V = 0.24/1.7 = 0.1412
[formate] = mol/V =0.18 /1.7 = 0.1059
then
pH = pKa + log(formate/formic acid)
pH = 3.75 + log(0.1059/0.1412)
pH = 3.625
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