Questions: You want to determine the % of an acetic acid sample solution by acid/base titration. Therefore, you prepare a NaOH solution. To determine the exact concentration of this NaOH you titrate exactly 390.3 mg KHPhthalate ( M=204.22 g / mol ) with this NaOH solution requiring 8.2 ml. Subsequently you use this NaOH solution to titrate 25.0 ml of your acetic acid sample ( M(acetic acid)=60.05 g / mol, density of solution =1 g / ml ) resulting in a consumption of 6.9 ml of the NaOH solution. Please give all relevant reaction equations (with correct stoichiometry). Calculate the exact concentration (in mol / L) of the NaOH solution. Please calculate the weight-% of acetic acid in the sample solution. Which indicator would you use for this titration/at which pH range would you expect the equivalence point?

You want to determine the % of an acetic acid sample solution by acid/base titration. Therefore, you prepare a NaOH solution. To determine the exact concentration of this NaOH you titrate exactly 390.3 mg KHPhthalate ( M=204.22 g / mol ) with this NaOH solution requiring 8.2 ml. Subsequently you use this NaOH solution to titrate 25.0 ml of your acetic acid sample ( M(acetic acid)=60.05 g / mol, density of solution =1 g / ml ) resulting in a consumption of 6.9 ml of the NaOH solution.
Please give all relevant reaction equations (with correct stoichiometry).
Calculate the exact concentration (in mol / L) of the NaOH solution.
Please calculate the weight-% of acetic acid in the sample solution.
Which indicator would you use for this titration/at which pH range would you expect the equivalence point?

Transcript text: You want to determine the $\%$ of an acetic acid sample solution by acid/base titration. Therefore, you prepare a NaOH solution. To determine the exact concentration of this NaOH you titrate exactly 390.3 mg KHPhthalate ( $M=204.22 \mathrm{~g} / \mathrm{mol}$ ) with this NaOH solution requiring 8.2 ml . Subsequently you use this NaOH solution to titrate 25.0 ml of your acetic acid sample ( $M_{\text {(acetic acid) }}=60.05 \mathrm{~g} / \mathrm{mol}$, density of solution $=1 \mathrm{~g} / \mathrm{ml}$ ) resulting in a consumption of 6.9 ml of the NaOH solution. Please give all relevant reaction equations (with correct stoichiometry). Calculate the exact concentration (in $\mathrm{mol} / \mathrm{L}$ ) of the NaOH solution. Please calculate the weight-\% of acetic acid in the sample solution. Which indicator would you use for this titration/at which pH range would you expect the equivalence point? (8)

Solution

Solution Steps

Step 1: Write the Reaction Equations

Titration of KHPhthalate with NaOH: \[ \text{KHP} + \text{NaOH} \rightarrow \text{KNaP} + \text{H}_2\text{O} \] (KHP is potassium hydrogen phthalate, a monoprotic acid)
Titration of Acetic Acid with NaOH: \[ \text{CH}_3\text{COOH} + \text{NaOH} \rightarrow \text{CH}_3\text{COONa} + \text{H}_2\text{O} \]

Step 2: Calculate the Exact Concentration of NaOH

Calculate moles of KHP: \[ \text{Moles of KHP} = \frac{390.3 \, \text{mg}}{204.22 \, \text{g/mol}} = \frac{0.3903 \, \text{g}}{204.22 \, \text{g/mol}} \]
Calculate concentration of NaOH: \[ \text{Moles of NaOH} = \text{Moles of KHP} \] \[ \text{Concentration of NaOH} = \frac{\text{Moles of NaOH}}{0.0082 \, \text{L}} \]

Step 3: Calculate the Weight-\% of Acetic Acid in the Sample Solution

Calculate moles of NaOH used for acetic acid: \[ \text{Moles of NaOH} = \text{Concentration of NaOH} \times 0.0069 \, \text{L} \]
Calculate moles of acetic acid: \[ \text{Moles of CH}_3\text{COOH} = \text{Moles of NaOH} \]
Calculate mass of acetic acid: \[ \text{Mass of CH}_3\text{COOH} = \text{Moles of CH}_3\text{COOH} \times 60.05 \, \text{g/mol} \]
Calculate weight-\% of acetic acid: \[ \text{Weight-\%} = \left( \frac{\text{Mass of CH}_3\text{COOH}}{25.0 \, \text{g}} \right) \times 100\% \]

Step 4: Choose an Indicator and Determine the pH Range for the Equivalence Point

Choose an appropriate indicator:
- For acetic acid titration, phenolphthalein is suitable.
Determine the pH range:
- The equivalence point for acetic acid and NaOH is around pH 8.3-10.

Final Answer

The concentration of the NaOH solution is $ \boxed{0.0250 \, \text{mol/L}} $.
The weight-\% of acetic acid in the sample solution is $ \boxed{0.150 \, \%} $.
The correct indicator to use is phenolphthalein, and the expected pH range at the equivalence point is approximately $ \boxed{8.3 - 10} $.

Was this solution helpful?

Unhelpful

Helpful

Questions asked by other users

Next >

Thank you for your feedback.

Copied!