HEPES can be used to buffer pH 6.5 to 8.5. What is the Ka of HEPES?

1) Can't determine from the information provided
2) 7.5 M
3) 7.5 x 10⁻⁶ M
4) 3.2 M
5) 3.2 x 10⁻⁸ M

The pKa value of HEPES is 7.48, which leads to a Ka value of 3.2 x 10^-8 M, making it an effective buffer in the pH range of 6.5 to 8.5. To calculate the moles of conjugate base in a buffer solution, the Henderson-Hasselbalch equation would be used.

Explanation:

The pKa value is essential to determine the acid dissociation constant (Ka) of HEPES. Using the provided pKa value of 7.48 for HEPES, the Ka can be calculated using the formula Ka = 10-pKa. Calculating the Ka for HEPES gives 3.2 x 10-8 M, which corresponds to option 5. This Ka value indicates that HEPES can effectively buffer within the pH range of approximately 6.5 to 8.5.

Regarding part (b) of the question about the number of moles of the conjugate base form of HEPES in a solution, the Henderson-Hasselbalch equation can be used. For a 175 mM solution of HEPES at pH 8.0, the ratio of conjugate base (A-) to acid (HA) is needed. The equation for this is pH = pKa + log([A-]/[HA]), which allows us to solve for the concentration of the conjugate base. This calculation requires further information on the total concentration of the acid and base form of HEPES in the solution.

HEPES can be used to buffer pH 6.5 to 8.5. What is the Ka of HEPES?1) Can't determine from the information provided 2) 7.5 M 3) 7.5 x 10⁻⁶ M 4) 3.2 M 5) 3.2 x 10⁻⁸ M

Answer :

Final answer:

Explanation:

Other Questions

HEPES can be used to buffer pH 6.5 to 8.5. What is the Ka of HEPES?

1) Can't determine from the information provided
2) 7.5 M
3) 7.5 x 10⁻⁶ M
4) 3.2 M
5) 3.2 x 10⁻⁸ M