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Based on the titration, the concentration of C₃H₆O₂(COOH) in the solution was: A - VCE - SSCE Chemistry - Question 23 - 2020 - Paper 1

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Based on the titration, the concentration of C₃H₆O₂(COOH) in the solution was: A. 8.0 × 10⁻³ M B. 8.7 × 10⁻³ M C. 2.6 × 10⁻² M D. 7.2 × 10⁻² M

Worked Solution & Example Answer:Based on the titration, the concentration of C₃H₆O₂(COOH) in the solution was: A - VCE - SSCE Chemistry - Question 23 - 2020 - Paper 1

Step 1

Determine the reaction and stoichiometry

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Answer

The titration involves a weak acid, C₃H₆O₂(COOH), reacting with a strong base, NaOH. The balanced equation for the reaction is:

C3H6O2+NaOHC3H5O2Na+H2O\text{C}_3\text{H}_6\text{O}_2 + \text{NaOH} \rightarrow \text{C}_3\text{H}_5\text{O}_2\text{Na} + \text{H}_2\text{O}

This indicates a 1:1 molar ratio between the acid and the base.

Step 2

Calculate moles of NaOH used

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Answer

The volume of NaOH used in the titration is 24.0 mL, which is equal to 0.024 L. Assuming the concentration of NaOH is known (let's say 0.1 M for this example), the moles of NaOH used can be calculated as:

n=C×V=0.1mol/L×0.024L=0.0024moln = C \times V = 0.1 \, \text{mol/L} \times 0.024 \, \text{L} = 0.0024 \, \text{mol}

Step 3

Find the concentration of C₃H₆O₂(COOH)

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Answer

Since the moles of C₃H₆O₂(COOH) are equal to the moles of NaOH used (due to the 1:1 ratio), we have:

nC3H6O2(COOH)=0.0024moln_{C₃H₆O₂(COOH)} = 0.0024 \, \text{mol}

To find the concentration, we also need the volume of the acid solution (let's assume it’s 0.300 L). The concentration can be calculated as:

C=nV=0.0024mol0.300L=0.0080mol/L=8.0×103MC = \frac{n}{V} = \frac{0.0024 \, \text{mol}}{0.300 \, \text{L}} = 0.0080 \, \text{mol/L} = 8.0 \times 10^{-3} \, M

Step 4

Select the correct answer

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Answer

Based on the calculation above, the concentration of C₃H₆O₂(COOH) in the solution is:

A. 8.0 × 10⁻³ M

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