Question

2) Buffers are extremely important in biology as they allow you to prepare solutions with a specific pH that can match physiological conditions. To prepare a buffer, we frequently take a weak acid and react it with a strong base.

2a) In this reaction, we combine 1 ml of 0.1 M NaOH with 10 ml 1M CH3CO2H (acetic acid). Write the reaction that proceeds (it goes to completion) and determine the amount of each component.

2b) Using the Henderson-Hasslebach equation we can determine the pH of the resulting solution. The Ka of Acetic Acid is 1.8 ∗ 10−5

henderson hasslebach equation: pH = pKa + log10([A-]/[HA])

2c) Is the resulting solution acidic or basic?

Answer 1

the reaction requires more then or equal 10 ml of NaOH to proceed

the amount of NaOH required (1ml) is 4 mg (for preparation of 1000 ml 0.1 M NaOH solution we need 4 gm or 4000 mg)

the amount of Acetic acid required (10 ml) is 605 mg ( for preparation of 1000 ml 1M Acetic acid solution 60.50 gm)

from the Henderson-Hasslebach equation the pH is calculated as follows

pH = pKa + log (CH₃COO^-)/(Na⁺)

= -log1.8 x 10^-5 + log (0.605)/(0.004)

= 3.744 + log (151.25)

= 3.744 + 2.178

pH = 5.923

So the resulting solution is acid in nature