Question

Now we need to prepare a buffer that has a pH of 7.4. We need this specific pH to

maintain our blood cells in culture. How should you prepare this buffer?
a) By mixing strong acid and then adjusting the pH with strong base
b) By mixing weak base with its conjugate acid and then adjusting the pH with strong
acid
c) By mixing weak acid with its conjugate base and then adjusting the pH with strong
base
d) By mixing strong base and then adjusting the pH with strong acid

Answer 1

A buffer with a pH of 7.4 should be prepared by mixing a weak acid with its conjugate base, and adjusting the pH with a strong base if needed, to ensure stability against pH changes when strong acids or bases are added.

Step-by-step explanation:

To prepare a buffer with a specific pH, such as the desired pH of 7.4 for maintaining blood cells in culture, one should mix a weak acid with its conjugate base and then adjust the pH with a strong base if necessary. This is because a buffer solution consists of a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid, which resists changes in pH upon the addition of small amounts of strong acids or bases.

For this task, the correct answer is therefore (c): By mixing weak acid with its conjugate base and then adjusting the pH with strong base. A well-known buffer system that operates around pH 7.4 is the bicarbonate buffer system, which consists of carbonic acid (a weak acid) and bicarbonate (the conjugate base).

Answer 2

b) By mixing weak base with its conjugate acid and then adjusting the pH with strong acid.

Step-by-step explanation:

Hello,

In this case, considering that the buffer required a pH greater than 7 where the basic conditions are present, we need a weak base and its conjugate base in order to assure such pH greater than 7. Moreover, by using a strong acid, we can gently add it in order to decrease the pH up to 7.4 via a properly measured neutralization of the necessary moles of base up to a hydrogen concentration of 3.98x10⁻⁸ (pH). Therefore, answer is b) By mixing weak base with its conjugate acid and then adjusting the pH with strong acid.

Best regards.