Question

Q1) We need to study an enzyme activity that works best at pH equals to 4,Which one of the following you will choose?

Buffer name pka Buffer capacity
Acetic acid 4.32 3.32-5.32
TRIS 8.1 7.1-9.1


Q2) The pka of carbonic acid is 6.37. At which ranges of pH carbonic acid can work as a good buffer?
H2CO3 —> HCO3- + H+


Q3) The most effective buffer is obtained when [------] = [------] and thus pH = pka


Q4) When the pH of the solution is below the pka of the wk acid / or wk base, what is the predominant form of the buffer, is it the basic form or the acidic form? The protonated form or the deprotonated form?

Answer 1

Answered By Unish ©

Verified Answer ✅

Step-by-step explanation:

Q1) For an enzyme activity that works best at pH 4, we would choose the buffer with a pKa closest to the desired pH. In this case, the buffer with acetic acid would be the best choice since its pKa of 4.32 is closest to pH 4.

Q2) A buffer is most effective when the pH is within 1 unit of its pKa. For the carbonic acid buffer system, the pKa is 6.37. Therefore, the buffer will work best at a pH range between 5.37 and 7.37. At a pH below 5.37, the buffer will be mostly in the protonated form (H2CO3), and at a pH above 7.37, the buffer will be mostly in the deprotonated form (HCO3-).

Q3) The most effective buffer is obtained when the concentration of the weak acid (HA) is equal to the concentration of its conjugate base (A-), and thus the pH is equal to the pKa of the buffer. This is because the buffer can neutralize added acid or base without causing a large change in pH.

Q4) When the pH of the solution is below the pKa of the weak acid (or weak base), the predominant form of the buffer will be the protonated form (HA) since at this pH, the weak acid has not yet donated a proton to become its conjugate base. Therefore, the buffer will be in the acidic form (HA), and will be able to accept protons to counteract any added base.