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The student collected 5.97 g of cyclohexene in the experiment - AQA - A-Level Chemistry - Question 3 - 2018 - Paper 3

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The student collected 5.97 g of cyclohexene in the experiment. Calculate the percentage yield of cyclohexene.

Worked Solution & Example Answer:The student collected 5.97 g of cyclohexene in the experiment - AQA - A-Level Chemistry - Question 3 - 2018 - Paper 3

Step 1

Calculate moles of cyclohexanol

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Answer

To find the moles of cyclohexanol used, apply the formula:

Moles=massmolar mass\text{Moles} = \frac{\text{mass}}{\text{molar mass}}

Given:

  • Density of cyclohexanol = 0.96 g/cm³
  • Volume used = 10 cm³
  • Molar mass of cyclohexanol = 100.16 g/mol

Mass of cyclohexanol: mass=density×volume=0.96 g/cm3×10 cm3=9.6 g\text{mass} = \text{density} \times \text{volume} = 0.96 \text{ g/cm}^3 \times 10 \text{ cm}^3 = 9.6\text{ g}

Now, calculate moles: Moles of cyclohexanol=9.6 g100.16 g/mol≈0.096 mol\text{Moles of cyclohexanol} = \frac{9.6\text{ g}}{100.16\text{ g/mol}} \approx 0.096\text{ mol}

Step 2

Calculate theoretical yield of cyclohexene

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Answer

According to the reaction:

1 mole of cyclohexanol produces 1 mole of cyclohexene\text{1 mole of cyclohexanol produces 1 mole of cyclohexene}

Thus, the theoretical yield of cyclohexene in grams is:

  • Molar mass of cyclohexene = 82.15 g/mol

Theoretical yield: mass of cyclohexene=moles×molar mass=0.096 mol×82.15 g/mol≈7.88 g\text{mass of cyclohexene} = \text{moles} \times \text{molar mass} = 0.096\text{ mol} \times 82.15\text{ g/mol} \approx 7.88\text{ g}

Step 3

Calculate percentage yield

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Answer

Now, use the formula for percentage yield:

Percentage yield=(actual yieldtheoretical yield)×100\text{Percentage yield} = \left(\frac{\text{actual yield}}{\text{theoretical yield}}\right) \times 100

Given:

  • Actual yield = 5.97 g
  • Theoretical yield = 7.88 g

Substituting these values: Percentage yield=(5.977.88)×100≈75.8%\text{Percentage yield} = \left(\frac{5.97}{7.88}\right) \times 100 \approx 75.8\%

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