Answer:pKa between 6 and 8
b. highly water soluble
c. minimally permeable to biological membranes
d. minimal effects of salt concentration
Explanation:
Since most biological reactions occur at near neutral pH of 6-8, good buffers should have their pKa around this region. A good buffer must also be water soluble and not easily permeable to biological membranes to avoid to avoid accumulation of the buffer compound in cells. The buffer should also not be highly ionic to prevent issues due to salt effects.