DATA TABLE Buffer A Buffer B Mass of NaC 2 H 3 O 2 used to prepare buffer (g) 0.
ID: 534935 • Letter: D
Question
DATA TABLE
Buffer A
Buffer B
Mass of NaC2H3O2 used to prepare buffer (g)
0.149 g
1.49 g
Volume of buffer prepared (mL)
100.0
100.0
Molar concentration of HC2H3O2 in buffer (M)
0.1
1.0
Initial pH of buffer
4.24
4.33
Volume of 0.5 M NaOH to raise pH by 2 units (mL)
1.5
19.0
Volume of 0.5 M HCl to lower pH by 2 units (mL)
1.0
5.0
Volume of 0.5 M NaOH at equivalence point (mL)
1.75
19.75
2. Buffer capacity has a rather loose definition, yet it is an important property of buffers. A commonly seen definition of buffer capacity is: “The amount of H+ or OH– that can be neutralized before the pH changes to a significant degree.” Use your data to determine the buffer capacity of Buffer A and Buffer B.
Buffer A
Buffer B
Mass of NaC2H3O2 used to prepare buffer (g)
0.149 g
1.49 g
Volume of buffer prepared (mL)
100.0
100.0
Molar concentration of HC2H3O2 in buffer (M)
0.1
1.0
Initial pH of buffer
4.24
4.33
Volume of 0.5 M NaOH to raise pH by 2 units (mL)
1.5
19.0
Volume of 0.5 M HCl to lower pH by 2 units (mL)
1.0
5.0
Volume of 0.5 M NaOH at equivalence point (mL)
1.75
19.75
Explanation / Answer
From the data table, we see that buffer B has a higher buffering capacity than buffer A.
This is because volume of NaOH needed to change the buffer by 2 units is only 1.5 mL while it is 19 mL for buffer B.
Thismeans that more number of moles of NaOH are needed to change the pH of buffer B, which means it has a stronger resistance to changes in its pH. This means it has higher buffering capacity.
In order to calculate the buffering capacity as per the definition, kindly define the term 'significant change' in pH, because by significant you could mean 0.1 unit or 0.5 unit or 1 unit, and the answer will vary accordingly.
Hope this helps !
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