17. You need to conduct an experiment in the laboratory. This requires that you prepare 500 ml of  sodium acetate buffer with pH = 4.30. In laboratory you have  solution of CH3COOH (pKa = 4.75), and a stock of CH3COONa.3H2O (MW=136.082 g/mol). Using the Henderson-Hasselbach equation and the mass balance and the ionization equation below, calculate how to prepare this buffer. Assume that the preparation consists of weighing out the necessary amounts of the compounds, or pipetting the required volume of the stock solution available. These are subsequently dissolved in water, and the buffer is prepared in a volumetric flask.

To prepare the sodium acetate buffer with pH = 4.30, we can use the Henderson-Hasselbalch equation, which relates the pH of a buffer solution to the pKa and the concentration of the acid and its conjugate base.

The Henderson-Hasselbalch equation is given by:

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

In this case, the acid is acetic acid (CH3COOH) and its conjugate base is sodium acetate (CH3COONa). The pKa of acetic acid is given as 4.75.

To calculate the required amounts, we need to understand the ionization equation of acetic acid:

CH3COOH ⇌ CH3COO- + H+

From the equation, we can see that one molecule of acetic acid (HA) produces one acetate ion (A-) and one hydrogen ion (H+).

Now, let's break down the steps to calculate how to prepare the buffer:

Step 1: Choose the volume and concentration

We need to prepare 500 ml of sodium acetate buffer. The concentration of the buffer is not given, so we can assume a concentration of 0.1 M for both acetic acid and sodium acetate.

Step 2: Calculate the required amounts

We can calculate the required amounts of acetic acid (CH3COOH) and sodium acetate (CH3COONa) using the Henderson-Hasselbalch equation.

Let's assume x moles of acetic acid and x moles of sodium acetate are required.

pH = pKa + log([A-]/[HA])
4.30 = 4.75 + log([CH3COO-]/[CH3COOH])

Since the concentration of acetic acid and sodium acetate is the same (0.1 M), we can substitute these values into the equation:

4.30 = 4.75 + log(x/x)
4.30 = 4.75 + log(1)

Therefore, x = 0.1 moles.

So, we need 0.1 moles of both acetic acid and sodium acetate to prepare the buffer.

Step 3: Calculate the required masses or volumes

Now, we need to calculate the required masses or volumes of acetic acid and sodium acetate.

Mass of acetic acid (CH3COOH):
Since the molecular weight of acetic acid is given (MW = 136.082 g/mol), we can calculate the mass of acetic acid required using the formula:

Mass = moles * MW
Mass = 0.1 moles * 136.082 g/mol
Mass = 13.6082 g

Therefore, we need approximately 13.61 grams of acetic acid.

The volume of sodium acetate stock solution (CH3COONa.3H2O):
To calculate the required volume of the stock solution, we need to know its concentration. If the concentration is given, we can use it to calculate the volume required. However, if the stock solution is assumed to be a saturated solution (maximum concentration), we need to determine its concentration first.

Given that the stock solution is assumed to be a saturated solution, you can add an excess amount of sodium acetate (CH3COONa.3H2O) to water and dissolve it until no more solid sodium acetate can dissolve. Weigh the resulting solution and calculate its concentration. Let's assume the concentration is found to be 0.2 M.

To calculate the required volume, we can use the formula:

Volume = moles / concentration
Volume = 0.1 moles / 0.2 M
Volume = 0.5 L = 500 ml

Therefore, to prepare the buffer solution, you need approximately 13.61 grams of acetic acid (CH3COOH) and 500 ml of a 0.2 M sodium acetate stock solution (CH3COONa.3H2O). Dissolve the acetic acid and the sodium acetate in water, and then make up the total volume to 500 ml in a volumetric flask.