What is the expected initial pH for Buffer 1 and Buffer 2 based on the given data?
The expected initial pH for Buffer 1 is 4.54, and for Buffer 2 is 4.94. These values were calculated using the Henderson-Hasselbalch equation based on the volume and concentration of the acid and salt in each buffer.
Acetate Buffer Composition
Buffer 1, which is an Acetate buffer, is composed of 15 mL of 0.10 M HC2H2O2 and 10 mL of 0.10 M NaC2H2O2 in a 25 mL volumetric flask. On the other hand, Buffer 2, also an Acetate buffer, consists of 10 mL of 0.50 M HC2H302 and 15 mL of 0.50 M NaC2H2O2 in a 25 mL volumetric flask.
Henderson-Hasselbalch Equation
The Henderson-Hasselbalch equation, pH = pKa + log {[A-]/[HA]}, was used to determine the expected initial pH values for both Buffer 1 and Buffer 2. In this equation, [A-] represents the concentration of the salt (NaC2H2O2), [HA] is the concentration of the acid (HC2H2O2), and pKa is the acid dissociation constant of the acid.
Calculation for Buffer 1:
For Buffer 1, the calculations involve finding the number of moles of HC2H2O2, NaC2H2O2, and subsequently determining the concentrations of the acid and salt in the buffer solution. The pKa value for HC2H2O2 is 4.76, which was used in the Henderson-Hasselbalch equation to obtain an expected initial pH of 4.54 for Buffer 1.
Calculation for Buffer 2:
For Buffer 2, similar calculations were carried out to find the concentrations of HC2H302, NaC2H2O2, and pKa value for HC2H302. Plugging these values into the Henderson-Hasselbalch equation resulted in an expected initial pH of 4.94 for Buffer 2.
Therefore, based on the aforementioned calculations and formulas, it can be concluded that the expected initial pH for Buffer 1 and Buffer 2 is 4.54 and 4.94, respectively.