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You need to prepare 0.10L buffer with a pH of 3.74 and totalconcentration of 0.10M . Use appropriate conjugate acid-base pairof either 0.5 M HC2H3O2 and 0.5M NaC2H302 or 0.5 M HCOOH and 0.5MNaCOOH. Calculate appropriate volumes to be used.

Ka HC2H302 1.8X 10^-5

Ka HCOOH 1.77X 10^-4


How do I know which pair to use?

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Jamar Ferry
Jamar FerryLv2
28 Sep 2019

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Related questions

Using the chemicals
-0.50 M HC2H3O2
-0.50 M NaC2H3O2
-0.50 M HCOOH
-0.50 M NaCOOH

Create the following buffers..
Buffer 1: Prepare 0.100 L of a pH = 3.74 buffer with a total bufferstrength of 0.100 M
Buffer 2: Prepare 0.100 L of a pH = 4.04 buffer with a total bufferstrength of 0.100 M

Show calculations of the volumes of acid and base needed to createthe two target buffers. Label which acid/base pair is used for eachbuffer system, and once volumes are found write down the volume ofwater to be added.

Helpful values: pKa for formic acid = 3.74 and for acetic acid,4.74

Steps...

-Use to calculate expected pH

pH = pKa + log([base]/[acid]

-Given the information we can fnd the ratio of base:acid for agiven buffer

[buffer] = [acid] + [base]

where the two buffer component concentrations equal the totalbuffer strength

-Finally we determine the correct volumes of the conjugateacid/base pair to give desire concentration using

m1v1=m2v2

Write the Ka expression for acetic acid and formic acid used in Part B. In addition find the Ka values for acetic acid and formic acid and calculate their pKa values. Part B is noted as follows:

Prepare 0.100 L of each buffer in a 100 mL volumetric flask. Using a graduated cylinder measure the necessary volumes of acid, base, and water which you have calculated: Chemicals used: 0.50 M HC2H3O2, 0.50 M NaC2H3O2, 0.50 M HCOOH, 0.50 M NaCOOH

Buffer 1: Prepare 0.100 L of a pH = 3.74 buffer with a total buffer strenth of 0.100M

Buffer 2: Prepare 0.100 L of a pH = 4.04 buffer with a total buffer strenth of 0.100M

Buffer 3: Prepare 0.100 L of a pH = 4.44 buffer with a total buffer strenth of 0.100M

Buffer 4: Prepare 0.100 L of a pH = 5.04 buffer with a total buffer strenth of 0.100M

I know the pKa values are 3.75 and 4.75, but I have NO idea how to get to that point from this information. Help please!




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