Tris and its conjugate base would be the best buffer at pH 8.
Further Explanation:
Buffer solution:
The solutions that oppose any change in their pH on addition of small amounts of acid or base are called buffer solutions. These are formed wither by a weak base and its conjugate acid or a weak acid and its conjugate base.
Henderson-Hasselbalch equation for a buffer solution is as follows:
…… (1)
A buffer is most effective when the concentration of both acid and its conjugate base is the same. So equation (1) then modifies as follows:
…… (2)
Therefore a buffer works best if its pH becomes equal to
.
The formula to calculate
is as follows:
…… (3)
Here,
is the dissociation constant of acid.
Substitute
for
in equation (3) to calculate
of tris.
![\begin{aligned}{\text{p}}{K_{\text{a}}} &= - \log \left( {6.3 \times {{10}^{ - 9}}} \right)a\\&= 8.20\\\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%7B%5Ctext%7Bp%7D%7D%7BK_%7B%5Ctext%7Ba%7D%7D%7D%20%26%3D%20%20-%20%5Clog%20%5Cleft%28%20%7B6.3%20%5Ctimes%20%7B%7B10%7D%5E%7B%20-%209%7D%7D%7D%20%5Cright%29a%5C%5C%26%3D%208.20%5C%5C%5Cend%7Baligned%7D)
Substitute
for
in equation (3) to calculate
of MES.
![\begin{aligned}{\text{p}}{K_{\text{a}}} &= - \log \left( {7.9 \times {{10}^{ - 7}}} \right)\\&= 6.10\\\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%7B%5Ctext%7Bp%7D%7D%7BK_%7B%5Ctext%7Ba%7D%7D%7D%20%26%3D%20%20-%20%5Clog%20%5Cleft%28%20%7B7.9%20%5Ctimes%20%7B%7B10%7D%5E%7B%20-%207%7D%7D%7D%20%5Cright%29%5C%5C%26%3D%206.10%5C%5C%5Cend%7Baligned%7D)
Substitute
for
in equation (3) to calculate
of acetic acid.
Substitute
for
in equation (3) to calculate
of formic acid.
![\begin{aligned}{\text{p}}{K_{\text{a}}} &= - \log \left( {1.8 \times {{10}^{ - 4}}} \right)\\&= 3.74\\\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%7B%5Ctext%7Bp%7D%7D%7BK_%7B%5Ctext%7Ba%7D%7D%7D%20%26%3D%20-%20%5Clog%20%5Cleft%28%20%7B1.8%20%5Ctimes%20%7B%7B10%7D%5E%7B%20-%204%7D%7D%7D%20%5Cright%29%5C%5C%26%3D%203.74%5C%5C%5Cend%7Baligned%7D)
Substitute
for
in equation (3) to calculate
of HEPES.
![\begin{aligned}{\text{p}}{K_{\text{a}}}&= - \log \left( {3.2 \times {{10}^{ - 8}}} \right) \\&= 7.49\\\end{gathered}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%7B%5Ctext%7Bp%7D%7D%7BK_%7B%5Ctext%7Ba%7D%7D%7D%26%3D%20-%20%5Clog%20%5Cleft%28%20%7B3.2%20%5Ctimes%20%7B%7B10%7D%5E%7B%20-%208%7D%7D%7D%20%5Cright%29%20%5C%5C%26%3D%207.49%5C%5C%5Cend%7Bgathered%7D)
The value of
of tris is nearly equal to the required pH. So tris along with its conjugate base would be the best buffer at pH 8.
Learn more:
Write the chemical equation responsible for pH of buffer containing and : brainly.com/question/8851686
Reason for the acidic and basic nature of amino acid. brainly.com/question/5050077
Answer details:
Grade: High School
Chapter: Acid, base and salts
Subject: Chemistry
Keywords: tris, acetic acid, formic acid, MES, HEPES, pH, pKa, Henderson, best buffer, 7.49, 8.20, 4.74, 3.74, Ka.