Describe the preparation of 5 liters of a 0.3 M acetate buffer, pH 4.47, starting from a 2 M solution of acetic acid and a 2.5 M solution of KOH
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https://www.jiskha.com/questions/1840760/describe-preparation-of-5-liters-of-a-0-3-m-acetate-buffer-ph-4-47-starting-from-a-2-m
To prepare a 5 liter 0.3 M acetate buffer at pH 4.47, we will need to calculate the amounts of acetic acid and potassium acetate required. Here is the step-by-step procedure to achieve this:
Step 1: Calculate the moles of acetic acid needed:
By using the Molarity (M) formula, we can determine the number of moles (n) required.
Molarity (M) = Moles (n) / Volume (V)
Rearranging the formula, n = M × V.
n(acetic acid) = (0.3 M) × (5 L) = 1.5 moles of acetic acid.
Step 2: Calculate the volume of acetic acid needed:
To obtain the required 1.5 moles of acetic acid, we will use the concentration of the 2 M solution of acetic acid.
Molarity (M) = Moles (n) / Volume (V)
Rearranging the formula, V = n / M.
V(acetic acid) = (1.5 moles) / (2 M) = 0.75 L of acetic acid.
Step 3: Calculate the moles of potassium acetate needed:
Since KOH is a strong base and acetic acid is a weak acid, we will use the equation for the dissociation of acetic acid to calculate the number of moles of potassium acetate required for the buffer solution.
CH3COOH + KOH -> CH3COOK + H2O
The stoichiometry of this equation shows that for every mole of acetic acid, we need an equal number of moles of potassium acetate. Therefore, the 1.5 moles of acetic acid we calculated also corresponds to the moles of potassium acetate.
Step 4: Calculate the volume of potassium acetate needed:
To obtain the required 1.5 moles of potassium acetate, we will use the concentration of the 2.5 M solution of KOH.
Molarity (M) = Moles (n) / Volume (V)
Rearranging the formula, V = n / M.
V(KOH) = (1.5 moles) / (2.5 M) = 0.6 L of KOH.
Step 5: Complete the process:
To prepare the buffer, add 0.75 liters of acetic acid (2 M solution) and 0.6 liters of KOH (2.5 M solution) to a container. Then, add distilled water and adjust the pH to 4.47 using a pH meter or a pH-adjusting solution. Once the pH is at the desired value, make up the total volume to 5 liters with distilled water.
By following these steps, you will successfully prepare a 5 liter 0.3 M acetate buffer at pH 4.47 using a 2 M solution of acetic acid and a 2.5 M solution of KOH.