12) Calculate the pH of a solution that is made by mixing 0.80 L of 0.30 M formi
ID: 588532 • Letter: 1
Question
12) Calculate the pH of a solution that is made by mixing 0.80 L of 0.30 M formic acid (HCOOH, K 1.77X10') and 0.90 L of 0.20 M sodium formate (NaHCOO). [Hint: don't forget 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't need 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 L of water, wi all of the AgOH dissolve?Explanation / Answer
(13)
According to H-H equation:
pH = pKa + log(moles of salt/moles of acid)
In a buffer system, when a little amount of acid is added, the moles of salt increase and the moles of salt decrease by this small amount, and overall the ratio changes to a small extent as well. But because this ratio is inside a log term, so the overall change in pH value is extremely small. In ths way, a buffer stabilizes pH values.
(14)
Using equation:
M1*V1 = M2*V2
Putting values:
34.55*0.102 = 25*M2
Solving we get:
M2 = 0.141 M
Hope this helps !
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