\"Acid-base buffers are most effective when the target pH of the buffer solution
ID: 590017 • Letter: #
Question
"Acid-base buffers are most effective when the target pH of the buffer solution is close (within one unit) to the pKa of the conjugate acid in in the conjugate acid/base pair to be used in the buffer. This is called the buffer range for a particular acid/base system.
For the three questions below, select the two compounds from the list which could be most effectively combined to create a buffer at the target pH. You will not need to use all of the compounds - and should need to use each compound only once.:
1. pH 4 buffer
2. pH 7 buffer
3. pH 9 buffer
sodium acetate, Na(CH3COO)
pyridinium chloride, (C5H5NH)C
ammonium chloride, (NH4)C
ammonia, NH3
pyridine, C5H5N
formic acid, HCOOH
sodium formate, Na(HCOO)
hypochlorous acid, HCO
sodium hypochlorite, NaCO
-Please provide explanation with answer if possible :)
"Acid-base buffers are most effective when the target pH of the buffer solution is close (within one unit) to the pKa of the conjugate acid in in the conjugate acid/base pair to be used in the buffer. This is called the buffer range for a particular acid/base system.
For the three questions below, select the two compounds from the list which could be most effectively combined to create a buffer at the target pH. You will not need to use all of the compounds - and should need to use each compound only once.:
1. pH 4 buffer
2. pH 7 buffer
3. pH 9 buffer
sodium acetate, Na(CH3COO)
pyridinium chloride, (C5H5NH)C
ammonium chloride, (NH4)C
ammonia, NH3
pyridine, C5H5N
formic acid, HCOOH
sodium formate, Na(HCOO)
hypochlorous acid, HCO
sodium hypochlorite, NaCO
-Please provide explanation with answer if possible :)
Explanation / Answer
pyridinium chloride, (C5H5NH)C --> pKa = 8.75
ammonium chloride, (NH4)C --> pKa = 4.75
ammonia, NH3 --> pKa = 9.25
pyridine, C5H5N --> 5.25
formic acid, HCOOH --> pKa = 3.75
sodium formate, Na(HCOO) --> pKa = 10.25
hypochlorous acid, HCO --> pKa = 7.5
sodium hypochlorite, NaCO --> pKa = 14-7.5 = 6.5
now, compare:
1. pH 4 buffer -> pKa = 4 -->
ammonium chloride, (NH4)C --> pKa = 4.75
formic acid, HCOOH --> pKa = 3.75
2. pH 7 buffer -> pKa = 7
hypochlorous acid, HCO --> pKa = 7.5
sodium hypochlorite, NaCO --> pKa = 14-7.5 = 6.5
3. pH 9 buffer pKa = 9
pyridinium chloride, (C5H5NH)C --> pKa = 8.75
ammonia, NH3 --> pKa = 9.25
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