Questions: Repeat Experiment #2 using acetic acid unknown #2. Begin by measuring 5.00 mL of the unknown acetic acid solution using a 10 mL graduated cylinder. Add this to a 150 mL Erlenmeyer flask, along with 75.0 mL of water and 2 drops of phenolpthalein. Titrate the unknown using the 0.100 M NaOH solution. Perform this titration in triplicate, and report the average concentration of acetic acid determined from the three titrations.

Solution Steps

To determine the average concentration of acetic acid from the titration data, follow these steps:

For each titration, calculate the moles of NaOH used. The volume of NaOH solution used in each titration is needed, but since it's not provided, let's assume you have the volumes \( V_1 \), \( V_2 \), and \( V_3 \) in liters for the three titrations. The concentration of NaOH is given as 0.100 M.

\[ \text{Moles of NaOH} = \text{Volume of NaOH (L)} \times 0.100 \, \text{mol/L} \]

The reaction between acetic acid and NaOH is a 1:1 stoichiometry:

\[ \text{CH}_3\text{COOH} + \text{NaOH} \rightarrow \text{CH}_3\text{COONa} + \text{H}_2\text{O} \]

Thus, the moles of acetic acid are equal to the moles of NaOH used in each titration.

The concentration of acetic acid in the original solution can be calculated using the formula:

\[ \text{Concentration of acetic acid (M)} = \frac{\text{Moles of acetic acid}}{\text{Volume of acetic acid solution (L)}} \]

The volume of the acetic acid solution is 5.00 mL, which is 0.00500 L.

Calculate the concentration for each titration and then find the average:

\[ \text{Average concentration} = \frac{\text{Concentration}_1 + \text{Concentration}_2 + \text{Concentration}_3}{3} \]

Final Answer