without prior permission. Violators will be prosecuted. publisher\'s 212 Experim
ID: 509409 • Letter: W
Question
without prior permission. Violators will be prosecuted. publisher's 212 Experiment as pH Measurementa and The Properles 4 Farmie acid. HFor, has a value eyaal to about 1.8 x A sudenti, asked to prepare a buffer having 10 a pH of 3.55 from a solution of formic acid and a solution of,odium formate having the same make How many of the solution should she add 20 HFar solution to the to L of the buffer (see discussion of buffers.) NGF NaF mL. NaF ml. 5. How many ml of 0.10 M NaoH should the student add to 20 ml 0.10 M HFor if she wished to prepare a buffer with a pH of 3.55, the same as in Problem 4?Explanation / Answer
pH = 3.55
pKa = 3.74
millimoles of HF = 20 x 0.1 = 2
HF + NaOH ---------------> NaF + H2O
2 0.1V 0 0
2-0.1V 0 0.1 V
pH = pKa + log [NaF / HF]
3.55 = 3.74 + log [0.1 V / 2 - 0.1V]
[0.1 V / 2 - 0.1V] = 0.646
0.1 V = 1.29 - 0.0646 V
V = 7.84
volume of NaOH = 7.84 mL
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