Question

What is the ph of a buffer solution prepared by mixing equal volumes of 0.3 m in tris in the acid form and 0.15 m in tris in the basic form?

a. 6.55
b. 8.00
c. 7.25
d. 7.60

Answer 1

The pH of the buffer solution prepared by mixing equal volumes of 0.3 M Tris in the acid form and 0.15 M Tris in the basic form is 7.6, indicating a slightly basic solution.

Step-by-step explanation:

The pH of a buffer solution prepared by mixing equal volumes of 0.3 M Tris in the acid form (TrisH+ or TrisHCl) and 0.15 M Tris in the basic form (Tris or Tris base) can be calculated using the Henderson-Hasselbalch equation:

pH = pKa + log ([Tris base]/[TrisH+])

Since equal volumes of 0.3 M TrisH+ and 0.15 M Tris base are mixed, the concentration of Tris base will be halved due to dilution. The final concentrations of TrisH+ and Tris base in the solution will be:

• [TrisH+] = 0.3 M
• [Tris base] = 0.075 M (after dilution)

Now, we apply these concentrations to the Henderson-Hasselbalch equation using the pKa value for Tris, which is 8.1:

pH = 8.1 + log (0.075/0.3)

The calculated pH of the buffer solution is therefore 7.6, which indicates that the solution is somewhat basic, as the pH is slightly below the pKa value of Tris.