Say, for example, that you had prepared a Buffer C, in which you mixed 8.203 g of sodium acetate, NaC2H3O2, with 100.0 mL of 1.0 M acetic acid.
a. What would be the initial pH of Buffer C? HOW???????
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To determine the initial pH of Buffer C, we can use the Henderson-Hasselbalch equation. This equation relates the pH of a buffer solution to the pKa and the ratio of the concentrations of the conjugate acid and base components of the buffer.
The pKa of acetic acid is given as 4.76. We can use this value to calculate the ratio of acetic acid to sodium acetate in the buffer.
First, we need to convert the mass of sodium acetate (NaC2H3O2) to moles. The molar mass of sodium acetate is 82.03 g/mol.
Number of moles of sodium acetate = mass / molar mass
= 8.203 g / 82.03 g/mol
= 0.1000 mol
Now, we need to calculate the concentration of acetic acid (CH3COOH) in the buffer solution.
Concentration of acetic acid = moles / volume
= 0.1000 mol / 0.100 L
= 1.0 M
The ratio of acetic acid to sodium acetate is 1:1 because they react in a 1:1 ratio to form a buffer.
Using the Henderson-Hasselbalch equation:
pH = pKa + log(base/acid)
pH = 4.76 + log(1/1)
pH = 4.76
Therefore, the initial pH of Buffer C is 4.76.