You want to prepare a pH=4.50 using sodium acetate and glacial acetic acid. You have n hand 300 mL of 0.100 M sodium acetate. How many grams of glacial acetic acid should you add to prepare the buffer? (Ka of acetic acid is 1.8e-5 at: 25 degrees Celsius)

Use the Henderson-Hasselbalch equation.

4.5 = 4.74 + log(b)/(a)
Solve for B/A.
You know acid is 300 mL x 0.1M = 30 millimoles.
Solve for base in millimoles. I would then convert to mols and from the to grams.
Finally, put all of that back into the equation to check that you really do get a pH of 4.5.

To prepare the buffer solution with a desired pH, we need to use the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

Where pH is the desired pH of 4.50, pKa is the negative logarithm of the acid dissociation constant (Ka) of acetic acid, and [A-]/[HA] is the ratio of the concentration of the conjugate base (acetate ion) to the concentration of the acid (acetic acid).

From the given information, we know that the concentration of sodium acetate is 0.100 M, which provides us with the concentration of acetate ion. However, we need to calculate the concentration of acetic acid.

First, let's calculate the concentration of acetate ion ([A-]). Since sodium acetate dissociates completely in water, the concentration of acetate ion will be equal to the concentration of sodium acetate:

[A-] = 0.100 M

Next, we need to calculate the concentration of acetic acid ([HA]). We can start by using the formula:

Ka = [A-][H+]/[HA]

Since we have the concentration of acetate ion ([A-]) and the Ka value (1.8e-5), we can rearrange the formula to solve for [HA]:

[HA] = [A-][H+]/Ka

Assuming the concentration of H+ ions in a pH of 4.50 is 10^(-4.50) M (because pH = -log[H+]), we have:

[HA] = (0.100 M)(10^(-4.50) M)/(1.8e-5)

Now we can calculate the [HA] value.

Once we have the concentrations of [A-] and [HA], we can substitute them into the Henderson-Hasselbalch equation and solve for the ratio [A-]/[HA]:

4.50 = pKa + log([A-]/[HA])

Solving for log([A-]/[HA]), we have:

log([A-]/[HA]) = 4.50 - pKa

Finally, we can use the antilog function to find the actual ratio [A-]/[HA], and this will be the same as the concentration ratio [A-]/[HA].

Now, to find the grams of glacial acetic acid needed, we multiply the calculated concentration of [HA] by the volume of the solution (300 mL) and the molar mass of acetic acid (60.05 g/mol). This will give us the mass of glacial acetic acid required.